| **Fair Value Measurements - Carrying Values and Estimated Fair Values of Financial Instruments (Details) (USD $)In Millions, unless otherwise specified**                                                                                                                                                                                                                                                                            | Oct. 31, 2014                                                                                                                                                                                                                                                                                                                                                                                                                                                               | Oct. 31, 2013 | Apr. 30, 2014                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
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| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | $ 5,224us-gaap_LongTermDebt                                                                                                                                                                                                                                                                                                                                                                                                                                                 |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Retail Notes                                                                                                                                                                                                                                                                                                                                                                                                                         | 279us-gaap_LoansReceivableFairValueDisclosure/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                                                                                                                |               | 390us-gaap_LoansReceivableFairValueDisclosure/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                                                                                                           |  |   |
| Notes Receivable                                                                                                                                                                                                                                                                                                                                                                                                                     | 7us-gaap_NotesReceivableFairValueDisclosure/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                                                                                                                  |               | 13us-gaap_NotesReceivableFairValueDisclosure/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                                                                                                            |  |   |
| Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Retail Notes                                                                                                                                                                                                                                                                                                                                                                                                                         | 275us-gaap_LoansReceivableFairValueDisclosure/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember                                                                                                                                                                                                                                                                                                                             |               | 390us-gaap_LoansReceivableFairValueDisclosure/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember                                                                                                                                                                                                                                                                                                                        |  |   |
| Notes Receivable                                                                                                                                                                                                                                                                                                                                                                                                                     | 8us-gaap_NotesReceivableFairValueDisclosure/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember                                                                                                                                                                                                                                                                                                                               |               | 14us-gaap_NotesReceivableFairValueDisclosure/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember                                                                                                                                                                                                                                                                                                                         |  |   |
| Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Retail Notes                                                                                                                                                                                                                                                                                                                                                                                                                         | 0us-gaap_LoansReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                             |               | 0us-gaap_LoansReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                        |  |   |
| Notes Receivable                                                                                                                                                                                                                                                                                                                                                                                                                     | 0us-gaap_NotesReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                             |               | 0us-gaap_NotesReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                        |  |   |
| Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Retail Notes                                                                                                                                                                                                                                                                                                                                                                                                                         | 0us-gaap_LoansReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                             |               | 0us-gaap_LoansReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                        |  |   |
| Notes Receivable                                                                                                                                                                                                                                                                                                                                                                                                                     | 0us-gaap_NotesReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                             |               | 0us-gaap_NotesReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                        |  |   |
| Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Retail Notes                                                                                                                                                                                                                                                                                                                                                                                                                         | 279us-gaap_LoansReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                           |               | 390us-gaap_LoansReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                      |  |   |
| Notes Receivable                                                                                                                                                                                                                                                                                                                                                                                                                     | 7us-gaap_NotesReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                             |               | 13us-gaap_NotesReceivableFairValueDisclosure/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember                                                                                                                                                                                                                                       |  |   |
| Manufacturing Operations [Member]                                                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 2,958us-gaap_LongTermDebt/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                                                                                                                                                                         |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Financial Services Operations [Member]                                                                                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 2,266us-gaap_LongTermDebt/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                                                                                                                                                                                     |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Line of Credit [Member] | Manufacturing Operations [Member]                                                                                                                                                                                                                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 694us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                                                                                                                 |               | 693us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                                                                                                            |  |   |
| Line of Credit [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 704us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                         |               | 720us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                    |  |   |
| Line of Credit [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 694us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                               |               | 693us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                          |  |   |
| Line of Credit [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                      |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                 |  |   |
| Line of Credit [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                      |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                 |  |   |
| Line of Credit [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 704us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                    |               | 720us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                               |  |   |
| Line of Credit [Member] | Financial Services Operations [Member]                                                                                                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 1,242us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                                                                                                                           |               | 1,018us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                                                                                                                      |  |   |
| Line of Credit [Member] | Financial Services Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 1,214us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                   |               | 990us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                |  |   |
| Line of Credit [Member] | Financial Services Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 1,242us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                         |               | 1,018us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                    |  |   |
| Line of Credit [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                  |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                             |  |   |
| Line of Credit [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                  |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_LineOfCreditMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                             |  |   |
| Line of Credit [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Debt Of Majority Owned Dealerships [Member] | Manufacturing Operations [Member]                                                                                                                                                                                                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Debt Of Majority Owned Dealerships [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Debt Of Majority Owned Dealerships [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Debt Of Majority Owned Dealerships [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_DebtOfMajorityOwnedDealershipsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                        |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_DebtOfMajorityOwnedDealershipsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                   |  |   |
| Debt Of Majority Owned Dealerships [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_DebtOfMajorityOwnedDealershipsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                        |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_DebtOfMajorityOwnedDealershipsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                   |  |   |
| Debt Of Majority Owned Dealerships [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 30us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_DebtOfMajorityOwnedDealershipsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                       |               | 48us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_DebtOfMajorityOwnedDealershipsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                  |  |   |
| Financing Arrangements [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 22us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancingArrangementsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                     |               | 44us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancingArrangementsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                |  |   |
| Financing Arrangements [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 48us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancingArrangementsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                           |               | 73us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancingArrangementsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                      |  |   |
| Financing Arrangements [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancingArrangementsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                 |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancingArrangementsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                            |  |   |
| Financing Arrangements [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancingArrangementsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                 |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancingArrangementsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                            |  |   |
| Financing Arrangements [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 22us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancingArrangementsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                |               | 44us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancingArrangementsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                           |  |   |
| Tax Exempt Bond [Member] | Manufacturing Operations [Member]                                                                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 225us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                                                                                                                    |               | 225us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                                                                                                               |  |   |
| Tax Exempt Bond [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 232us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                            |               | 229us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                       |  |   |
| Tax Exempt Bond [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 225us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                  |               | 225us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                             |  |   |
| Tax Exempt Bond [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                         |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                    |  |   |
| Tax Exempt Bond [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 232us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                       |               | 229us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                  |  |   |
| Tax Exempt Bond [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                         |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                    |  |   |
| Promissory Note [Member] | Manufacturing Operations [Member]                                                                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 10us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= nav_PromissoryNoteMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                                                                                                                    |               | 20us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= nav_PromissoryNoteMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                                                                                                               |  |   |
| Promissory Note [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 10us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_PromissoryNoteMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                            |               | 20us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_PromissoryNoteMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                       |  |   |
| Promissory Note [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Promissory Note [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Promissory Note [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_PromissoryNoteMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                        |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_PromissoryNoteMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                   |  |   |
| Promissory Note [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 10us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_PromissoryNoteMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                       |               | 20us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_PromissoryNoteMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                  |  |   |
| Financed lease obligations [Member] | Manufacturing Operations [Member]                                                                                                                                                                                                                                                                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Financed lease obligations [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Financed lease obligations [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Financed lease obligations [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancedLeaseObligationsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                              |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancedLeaseObligationsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                         |  |   |
| Financed lease obligations [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancedLeaseObligationsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                              |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_FinancedLeaseObligationsMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                         |  |   |
| Financed lease obligations [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Notes Payable, Other Payables [Member] | Manufacturing Operations [Member]                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 29us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableOtherPayablesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                                                                                                     |               | 39us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableOtherPayablesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                                                                                                |  |   |
| Notes Payable, Other Payables [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Notes Payable, Other Payables [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Notes Payable, Other Payables [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableOtherPayablesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                         |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableOtherPayablesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                    |  |   |
| Notes Payable, Other Payables [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Notes Payable, Other Payables [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Secured Debt [Member] | Financial Services Operations [Member]                                                                                                                                                                                                                                                                                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 914us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= us-gaap_SecuredDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                                                                                                                              |               | 778us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= us-gaap_SecuredDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                                                                                                                         |  |   |
| Secured Debt [Member] | Financial Services Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Secured Debt [Member] | Financial Services Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 914us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_SecuredDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                            |               | 778us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_SecuredDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                       |  |   |
| Secured Debt [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_SecuredDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                   |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_SecuredDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                              |  |   |
| Secured Debt [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_SecuredDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                   |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_SecuredDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                              |  |   |
| Secured Debt [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 911us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_SecuredDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                 |               | 775us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_SecuredDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                            |  |   |
| Commercial Paper [Member] | Financial Services Operations [Member]                                                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 74us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                                                                                                                           |               | 21us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                                                                                                                      |  |   |
| Commercial Paper [Member] | Financial Services Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 74us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                   |               | 21us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                              |  |   |
| Commercial Paper [Member] | Financial Services Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 74us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                         |               | 21us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                    |  |   |
| Commercial Paper [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 74us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                             |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Commercial Paper [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               | 21us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                         |  |   |
| Commercial Paper [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                              |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Commercial Paper [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                          |  |   |
| Commercial Paper [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                              |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Commercial Paper [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_CommercialPaperMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                          |  |   |
| Borrowings Secured By Operating and Finance Leases [Member] | Financial Services Operations [Member]                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 36us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                                                                                                  |               | 49us-gaap_LongTermDebt/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                                                                                                             |  |   |
| Borrowings Secured By Operating and Finance Leases [Member] | Financial Services Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 36us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                          |               | 49us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                     |  |   |
| Borrowings Secured By Operating and Finance Leases [Member] | Financial Services Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 36us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                                |               | 49us-gaap_LongTermDebt/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                                                                                           |  |   |
| Borrowings Secured By Operating and Finance Leases [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                      |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                 |  |   |
| Borrowings Secured By Operating and Finance Leases [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                      |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                 |  |   |
| Borrowings Secured By Operating and Finance Leases [Member] | Financial Services Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 36us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                     |               | 49us-gaap_LongTermDebtFairValue/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= nav_BorrowingsSecuredByOperatingAndFinanceLeasesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                |  |   |
| Eight Point Two Five Percent Senior Notes [Member] | Notes Payable to Banks [Member] | Manufacturing Operations [Member]                                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 1,180us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                             |               | 1,178us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                                        |  |   |
| Eight Point Two Five Percent Senior Notes [Member] | Notes Payable to Banks [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 1,285us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                     |               | 1,274us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                |  |   |
| Eight Point Two Five Percent Senior Notes [Member] | Notes Payable to Banks [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 1,180us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                           |               | 1,178us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                      |  |   |
| Eight Point Two Five Percent Senior Notes [Member] | Notes Payable to Banks [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 1,285us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                |               | 1,274us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                           |  |   |
| Eight Point Two Five Percent Senior Notes [Member] | Notes Payable to Banks [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                    |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                               |  |   |
| Eight Point Two Five Percent Senior Notes [Member] | Notes Payable to Banks [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                    |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_EightPointTwoFivePercentSeniorNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableToBanksMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                               |  |   |
| Three Point Zero Percent Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member]                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 0us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                     |               | 544us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                              |  |   |
| Three Point Zero Percent Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               | 586us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                      | [1] |   |
| Three Point Zero Percent Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               | 544us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                            | [1] |   |
| Three Point Zero Percent Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               | 586us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember | [1] |   |
| Three Point Zero Percent Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember   | [1] |   |
| Three Point Zero Percent Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember   | [1] |   |
| Four Point Five Zero Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member]                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               | 177us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember                                                                                                                                                                                                                                                                   |  |   |
| Four Point Five Zero Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member]                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               | 177us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                         |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 181us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                       |               | 177us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                  |  |   |
| Four Point Five Zero Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 196us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                               | [1]           | 203us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                          | [1] |   |
| Four Point Five Zero Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 181us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                     | [1]           | 177us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                | [1] |   |
| Four Point Five Zero Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember            | [1]           | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember       | [1] |   |
| Four Point Five Zero Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember            | [1]           | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember       | [1] |   |
| Four Point Five Zero Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 196us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember          | [1]           | 203us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember     | [1] |   |
| Four Point Seven Five Senior Subordinated Convertible Notes [Member] [Member] | Convertible Subordinated Debt [Member]                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  | 367us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember |
| Four Point Seven Five Senior Subordinated Convertible Notes [Member] [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member]                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
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| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 371us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                                |               | 0us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                                                                                             |  |   |
| Four Point Seven Five Senior Subordinated Convertible Notes [Member] [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 413us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                        | [1]           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Four Point Seven Five Senior Subordinated Convertible Notes [Member] [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Reported Value Measurement [Member]                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt                                                                                                                                                                                                                                                                                                                                                                                                                       | 371us-gaap_LongTermDebt/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_CarryingReportedAmountFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                              | [1]           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Four Point Seven Five Senior Subordinated Convertible Notes [Member] [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel1Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember     | [1]           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Four Point Seven Five Senior Subordinated Convertible Notes [Member] [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | 0us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel2Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember     | [1]           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Four Point Seven Five Senior Subordinated Convertible Notes [Member] [Member] | Convertible Subordinated Debt [Member] | Manufacturing Operations [Member] | Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]                                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| **Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]**                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
| Long-term Debt, Fair Value                                                                                                                                                                                                                                                                                                                                                                                                           | $ 413us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_FairValueByFairValueHierarchyLevelAxis= us-gaap_FairValueInputsLevel3Member/ us-gaap_FairValueByMeasurementBasisAxis= us-gaap_EstimateOfFairValueFairValueDisclosureMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember | [1]           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |  |   |
|                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| [1]The carrying value represents the consolidated financial statement amount of the debt which excludes the allocation of the conversion feature to equity, while the fair value is based on quoted market prices for Level 1 convertible notes which include the equity feature and internally developed valuation techniques such as discounted cash flow modeling for Level 3 convertible notes which include the equity feature. |

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| - Definition
Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Glossary Loan -URI http://asc.fasb.org/extlink&oid=6517073
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 7Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.16) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 20, 22 -Article 5Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910
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| - Definition
The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.
+ References
No definition available.
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| - Definition
Fair value portion of an agreement for an unconditional promise by the maker to pay the holder a definite sum of money at a future date.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.3(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 3 -Subparagraph b -Article 5
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