| **Restructuring and Impairments - Restructuring Reserve by Type (Details) (USD $)In Millions, unless otherwise specified** | 6 Months Ended                                                                                                              |                                                                                                                             |                                                                                                          |
|----------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------|
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| **Restructuring Cost and Reserve [Line Items]**                                                                            |                                                                                                                        |                                                                                                                        |                                                                                                     |   |
| Restructuring Reserve                                                                                                      | $ 18us-gaap_RestructuringReserve                                                                                            | $ 30us-gaap_RestructuringReserve                                                                                            | $ 20us-gaap_RestructuringReserve                                                                         | $ 34us-gaap_RestructuringReserve |
| Restructuring and Related Cost, Incurred Cost                                                                              | 7us-gaap_RestructuringAndRelatedCostIncurredCost                                                                            | 11us-gaap_RestructuringAndRelatedCostIncurredCost                                                                           |                                                                                                     |   |
| Payments for Restructuring                                                                                                 | 8us-gaap_PaymentsForRestructuring                                                                                           | 15us-gaap_PaymentsForRestructuring                                                                                          |                                                                                                     |   |
| Restructuring Reserve, Accrual Adjustment                                                                                  | (1)us-gaap_RestructuringReserveAccrualAdjustment                                                                            | 0us-gaap_RestructuringReserveAccrualAdjustment                                                                              |                                                                                                     |   |
| Employee Severance [Member]                                                                                                |                                                                                                                        |                                                                                                                        |                                                                                                     |   |
| **Restructuring Cost and Reserve [Line Items]**                                                                            |                                                                                                                        |                                                                                                                        |                                                                                                     |   |
| Restructuring Reserve                                                                                                      | 10us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember                    | 16us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember                    | 8us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember  | 15us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember |
| Restructuring and Related Cost, Incurred Cost                                                                              | 7us-gaap_RestructuringAndRelatedCostIncurredCost/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember  | 9us-gaap_RestructuringAndRelatedCostIncurredCost/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember  |                                                                                                     |   |
| Payments for Restructuring                                                                                                 | 4us-gaap_PaymentsForRestructuring/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember                 | 8us-gaap_PaymentsForRestructuring/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember                 |                                                                                                     |   |
| Restructuring Reserve, Accrual Adjustment                                                                                  | (1)us-gaap_RestructuringReserveAccrualAdjustment/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember  | 0us-gaap_RestructuringReserveAccrualAdjustment/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember    |                                                                                                     |   |
| Employee Relocation [Member]                                                                                               |                                                                                                                        |                                                                                                                        |                                                                                                     |   |
| **Restructuring Cost and Reserve [Line Items]**                                                                            |                                                                                                                        |                                                                                                                        |                                                                                                     |   |
| Restructuring Reserve                                                                                                      |                                                                                                                        | 0us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeRelocationMember                    |                                                                                                     | 0us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeRelocationMember |
| Restructuring and Related Cost, Incurred Cost                                                                              |                                                                                                                        | 1us-gaap_RestructuringAndRelatedCostIncurredCost/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeRelocationMember |                                                                                                     |   |
| Payments for Restructuring                                                                                                 |                                                                                                                        | 1us-gaap_PaymentsForRestructuring/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeRelocationMember                |                                                                                                     |   |
| Restructuring Reserve, Accrual Adjustment                                                                                  |                                                                                                                        | 0us-gaap_RestructuringReserveAccrualAdjustment/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeRelocationMember   |                                                                                                     |   |
| Lease Vacancy [Member] [Domain]                                                                                            |                                                                                                                        |                                                                                                                        |                                                                                                     |   |
| **Restructuring Cost and Reserve [Line Items]**                                                                            |                                                                                                                        |                                                                                                                        |                                                                                                     |   |
| Restructuring Reserve                                                                                                      | 7us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= nav_LeaseVacancyMemberDomain                        | 15us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= nav_LeaseVacancyMemberDomain                       | 11us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= nav_LeaseVacancyMemberDomain    | 18us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= nav_LeaseVacancyMemberDomain |
| Restructuring and Related Cost, Incurred Cost                                                                              | 0us-gaap_RestructuringAndRelatedCostIncurredCost/ us-gaap_RestructuringCostAndReserveAxis= nav_LeaseVacancyMemberDomain     | 1us-gaap_RestructuringAndRelatedCostIncurredCost/ us-gaap_RestructuringCostAndReserveAxis= nav_LeaseVacancyMemberDomain     |                                                                                                     |   |
| Payments for Restructuring                                                                                                 | 4us-gaap_PaymentsForRestructuring/ us-gaap_RestructuringCostAndReserveAxis= nav_LeaseVacancyMemberDomain                    | 4us-gaap_PaymentsForRestructuring/ us-gaap_RestructuringCostAndReserveAxis= nav_LeaseVacancyMemberDomain                    |                                                                                                     |   |
| Restructuring Reserve, Accrual Adjustment                                                                                  | 0us-gaap_RestructuringReserveAccrualAdjustment/ us-gaap_RestructuringCostAndReserveAxis= nav_LeaseVacancyMemberDomain       | 0us-gaap_RestructuringReserveAccrualAdjustment/ us-gaap_RestructuringCostAndReserveAxis= nav_LeaseVacancyMemberDomain       |                                                                                                     |   |
| Other Restructuring [Member]                                                                                               |                                                                                                                        |                                                                                                                        |                                                                                                     |   |
| **Restructuring Cost and Reserve [Line Items]**                                                                            |                                                                                                                        |                                                                                                                        |                                                                                                     |   |
| Restructuring Reserve                                                                                                      | 1us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_OtherRestructuringMember                    | (1)us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_OtherRestructuringMember                  | 1us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_OtherRestructuringMember | 1us-gaap_RestructuringReserve/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_OtherRestructuringMember |
| Restructuring and Related Cost, Incurred Cost                                                                              | 0us-gaap_RestructuringAndRelatedCostIncurredCost/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_OtherRestructuringMember | 0us-gaap_RestructuringAndRelatedCostIncurredCost/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_OtherRestructuringMember |                                                                                                     |   |
| Payments for Restructuring                                                                                                 | 0us-gaap_PaymentsForRestructuring/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_OtherRestructuringMember                | 2us-gaap_PaymentsForRestructuring/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_OtherRestructuringMember                |                                                                                                     |   |
| Restructuring Reserve, Accrual Adjustment                                                                                  | $ 0us-gaap_RestructuringReserveAccrualAdjustment/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_OtherRestructuringMember | $ 0us-gaap_RestructuringReserveAccrualAdjustment/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_OtherRestructuringMember |                                                                                                     |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Discloses the amount charged against the accrued restructuring reserves, or earnings if not previously accrued, during the period for the specified type of restructuring cost.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 5.P.4(b)) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section P -Subsection 3, 4
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 5.P.4(b)) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section P -Subsection 3, 4
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of any reversal and other adjustment made during the period to the amount of a previously accrued liability for a specified type of restructuring cost, excluding adjustments for costs incurred during the period, costs settled during the period, and foreign currency translation adjustments.
+ References
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| X                                                                                                                                                                |
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