| **Debt - Narrative (Details) (USD $)**                                                                                                                                      | 3 Months Ended                                                                                                                                                                                                                                                                                               | 6 Months Ended                                                                                                                                                                                                                                                                          | 12 Months Ended                                                                                                                                                                                                                                                                                  | 1 Months Ended                                                                                                                                                                                                                                                                                               |
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| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Payments to subsidiary to meet convenant requirement                                                                                                                        |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   | $ 0nav_PaymentsToSubsidiaryToMeetConvenantRequirement | $ 0nav_PaymentsToSubsidiaryToMeetConvenantRequirement | $ 0nav_PaymentsToSubsidiaryToMeetConvenantRequirement |   |
| Warrants and Rights Outstanding                                                                                                                                             | 2,875,175us-gaap_WarrantsAndRightsOutstanding                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | 2,875,175us-gaap_WarrantsAndRightsOutstanding                                                                                                                                                                                                                                                                |   |   |   |   |   |
| Charge Related to Repurchase of Debt                                                                                                                                        |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    | 11,000,000nav_ChargeRelatedtoRepurchaseofDebt                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Shares of Call Options Unwound                                                                                                                                              |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    | 8,026,456nav_SharesofCallOptionsUnwound                                                                                                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Shares of Warrants Unwound                                                                                                                                                  | 1,939,376nav_SharesofWarrantsUnwound                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    | 6,523,319nav_SharesofWarrantsUnwound                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Payments of Debt Issuance Costs                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | 7,000,000us-gaap_PaymentsOfDebtIssuanceCosts                                                                                                                                                                                                                                                                 | 13,000,000us-gaap_PaymentsOfDebtIssuanceCosts |   |   |   |   |
| Cash Dividends Paid to Parent Company by Consolidated Subsidiaries                                                                                                          |                                                                                                                                                                                                                                                                                                         | 125,000,000us-gaap_CashDividendsPaidToParentCompanyByConsolidatedSubsidiaries                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Proceeds from issuance of securitized debt                                                                                                                                  |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | 250,000,000us-gaap_ProceedsFromIssuanceOfSecuredDebt                                                                                                                                                                                                                                                         | 152,000,000us-gaap_ProceedsFromIssuanceOfSecuredDebt |   |   |   |   |
| Three Point Zero Percent Senior Subordinated Convertible Notes [Member]                                                                                                     |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Shares of Warrants Unwound                                                                                                                                                  | 1,939,376nav_SharesofWarrantsUnwound/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember                                                                                                                                                                          |                                                                                                                                                                                                                                                                                    | 6,523,319nav_SharesofWarrantsUnwound/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember                                                                                                                                                              |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Four Point Seven Five Senior Subordinated Convertible Notes [Member] [Member]                                                                                               |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Option Indexed to Issuer's Equity, Strike Price                                                                                                                             |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | $ 54.07us-gaap_OptionIndexedToIssuersEquityStrikePrice1/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember                                                                                                                                                    |   |   |   |   |   |
| Debt Instrument, Convertible, Conversion Ratio                                                                                                                              |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | 18.4946us-gaap_DebtInstrumentConvertibleConversionRatio1/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember                                                                                                                                                   |   |   |   |   |   |
| Financial Services Operations [Member] | VFN Facility [Member]                                                                                                              |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Debt Instrument, Face Amount                                                                                                                                                |                                                                                                                                                                                                                                                                                                         | 500,000,000us-gaap_DebtInstrumentFaceAmount/ us-gaap_DebtInstrumentAxis= nav_VfnFacilityMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember                                                                                                            |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Financial Services Operations [Member] | Notes Payable, Other Payables [Member] | Investor Notes Maturing Two Thousand and Fifteen [Member]                                 |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Debt Instrument, Face Amount                                                                                                                                                |                                                                                                                                                                                                                                                                                                         | 250,000,000us-gaap_DebtInstrumentFaceAmount/ us-gaap_DebtInstrumentAxis= nav_InvestorNotesMaturingTwoThousandandFifteenMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableOtherPayablesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember      |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Financial Services Operations [Member] | Notes Payable, Other Payables [Member] | Investor Notes Maturing October Two Thousand Thirteen [Member]                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Debt Instrument, Face Amount                                                                                                                                                |                                                                                                                                                                                                                                                                                                         | 200,000,000us-gaap_DebtInstrumentFaceAmount/ us-gaap_DebtInstrumentAxis= nav_InvestorNotesMaturingOctoberTwoThousandThirteenMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_NotesPayableOtherPayablesMember/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Manufacturing Operations [Member] | Convertible Subordinated Debt [Member] | Three Point Zero Percent Senior Subordinated Convertible Notes [Member]                        |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Repayments of Long-term Debt                                                                                                                                                |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    | 404,000,000us-gaap_RepaymentsOfLongTermDebt/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember    |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Debt Instrument, Face Amount                                                                                                                                                |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   | 570,000,000us-gaap_DebtInstrumentFaceAmount/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember |
| Class of Warrant or Right, Exercise Price of Warrants or Rights                                                                                                             |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   | $ 60.14us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember |
| Proceeds from Issuance of Warrants                                                                                                                                          |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   | 87,000,000us-gaap_ProceedsFromIssuanceOfWarrants/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember |
| Manufacturing Operations [Member] | Convertible Subordinated Debt [Member] | Four Point Five Zero Senior Subordinated Convertible Notes [Member]                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Debt Instrument, Interest Rate, Stated Percentage                                                                                                                           | 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember        |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember        |   |   |   |   |   |
| Manufacturing Operations [Member] | Convertible Subordinated Debt [Member] | Four Point Seven Five Senior Subordinated Convertible Notes [Member] [Member]                  |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Debt Instrument, Interest Rate, Stated Percentage                                                                                                                           | 4.75%us-gaap_DebtInstrumentInterestRateStatedPercentage/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | 4.75%us-gaap_DebtInstrumentInterestRateStatedPercentage/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember |   |   |   |   |   |
| Debt Instrument, Face Amount                                                                                                                                                |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    | 411,000,000us-gaap_DebtInstrumentFaceAmount/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember |                                                                                                                                                                                                                                                                                                         | 411,000,000us-gaap_DebtInstrumentFaceAmount/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember |   |   |   |   |
| Manufacturing Operations [Member] | Tax Exempt Bond [Member]                                                                                                                |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Debt Instrument, Interest Rate, Stated Percentage                                                                                                                           | 6.50%us-gaap_DebtInstrumentInterestRateStatedPercentage/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                     |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | 6.50%us-gaap_DebtInstrumentInterestRateStatedPercentage/ us-gaap_LongtermDebtTypeAxis= nav_TaxExemptBondMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember                                                                                                                     |   |   |   |   |   |
| Call Option [Member] | Manufacturing Operations [Member] | Convertible Subordinated Debt [Member] | Three Point Zero Percent Senior Subordinated Convertible Notes [Member] |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Payments for Derivative Instrument, Investing Activities                                                                                                                    |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   | 125,000,000us-gaap_PaymentsForDerivativeInstrumentInvestingActivities/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_OptionIndexedToIssuersEquityEquityAxis= us-gaap_CallOptionMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember |
| Option Indexed to Issuer's Equity, Indexed Shares                                                                                                                           |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   | 11,337,870us-gaap_OptionIndexedToIssuersEquityIndexedShares/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_OptionIndexedToIssuersEquityEquityAxis= us-gaap_CallOptionMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember |
| Option Indexed to Issuer's Equity, Strike Price                                                                                                                             |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   | $ 50.27us-gaap_OptionIndexedToIssuersEquityStrikePrice1/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_OptionIndexedToIssuersEquityEquityAxis= us-gaap_CallOptionMember/ us-gaap_StatementBusinessSegmentsAxis= nav_ManufacturingOperationsMember |
| Convertible Debt Securities [Member] | Three Point Zero Percent Senior Subordinated Convertible Notes [Member]                                                              |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Option Indexed to Issuer's Equity, Strike Price                                                                                                                             |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   | $ 50.27us-gaap_OptionIndexedToIssuersEquityStrikePrice1/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis= us-gaap_ConvertibleDebtSecuritiesMember/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember |
| Debt Instrument, Convertible, Conversion Ratio                                                                                                                              |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | 19.891us-gaap_DebtInstrumentConvertibleConversionRatio1/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis= us-gaap_ConvertibleDebtSecuritiesMember/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember         |   |   |   |   |   |
| Convertible Debt Securities [Member] | Four Point Five Zero Senior Subordinated Convertible Notes [Member]                                                                  |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Debt Instrument, Convertible, Conversion Ratio                                                                                                                              |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | 17.1233us-gaap_DebtInstrumentConvertibleConversionRatio1/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis= us-gaap_ConvertibleDebtSecuritiesMember/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember            |   |   |   |   |   |
| Mexican Pesos                                                                                                                                                               |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Long-term Debt                                                                                                                                                              |                                                                                                                                                                                                                                                                                                         | 1,800,000,000us-gaap_CommercialPaper/ nav_CurrencyDenominationAxis= currency_MXN                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| United States of America, Dollars                                                                                                                                           |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| **Debt Instrument [Line Items]**                                                                                                                                            |                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                                         |   |   |   |   |   |
| Long-term Debt                                                                                                                                                              | $ 118,000,000us-gaap_CommercialPaper/ nav_CurrencyDenominationAxis= currency_USD                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                             | $ 118,000,000us-gaap_CommercialPaper/ nav_CurrencyDenominationAxis= currency_USD                                                                                                                                                                                                                             |   |   |   |   |   |

| X                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Charge Related to Repurchase of Debt
+ References
No definition available.
+ Details**Name:**nav_ChargeRelatedtoRepurchaseofDebt**Namespace Prefix:**nav_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Payments to subsidiary to meet convenant requirement
+ References
No definition available.
+ Details**Name:**nav_PaymentsToSubsidiaryToMeetConvenantRequirement**Namespace Prefix:**nav_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Shares of Call Options Unwound
+ References
No definition available.
+ Details**Name:**nav_SharesofCallOptionsUnwound**Namespace Prefix:**nav_**Data Type:**xbrli:sharesItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Shares of Warrants Unwound
+ References
No definition available.
+ Details**Name:**nav_SharesofWarrantsUnwound**Namespace Prefix:**nav_**Data Type:**xbrli:sharesItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents disclosure of the aggregate cash dividends paid to the entity by consolidated subsidiaries.
+ References
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| - Definition
Exercise price per share or per unit of warrants or rights outstanding.
+ References
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| - Definition
Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.
+ References
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| - Definition
Face (par) amount of debt instrument at time of issuance.
+ References
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| - Definition
Contractual interest rate for funds borrowed, under the debt agreement.
+ References
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| - Definition
The number of issuer's shares to which the option contract is indexed.
+ References
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| - Definition
Exercise or strike price stated in the contract for options indexed to the issuer's equity shares.
+ References
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| - Definition
The cash outflow for derivative instruments during the period, which are classified as investing activities, excluding those designated as hedging instruments.
+ References
No definition available.
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| - Definition
The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.
+ References
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| - Definition
The cash inflow from amounts received from issuance of long-term debt that is wholly or partially secured by collateral. Excludes proceeds from tax exempt secured debt.
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| - Definition
The cash inflow from issuance of rights to purchase common shares at predetermined price (usually issued together with corporate debt).
+ References
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| - Definition
The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer.
+ References
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| - Definition
Value of outstanding derivative securities that permit the holder the right to purchase securities (usually equity) from the issuer at a specified price.
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