| **Restructuring and Impairments - Narrative (Details) (USD $)In Millions, unless otherwise specified** | 3 Months Ended                                                                                                                                                                                                                             | 6 Months Ended                                                                                                                   | 3 Months Ended                                                                                                                                                                                                                             |                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------|
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| **Restructuring Cost and Reserve [Line Items]**                                                        |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| Restructuring charges                                                                                  | $ 6us-gaap_RestructuringCharges                                                                                                                                                                                                            | $ 8us-gaap_RestructuringCharges                                                                                                  | $ 9us-gaap_RestructuringCharges                                                                                                                                                                                                            | $ 11us-gaap_RestructuringCharges                                                                                                 |   |   |
| Asset impairment charges                                                                               | 1us-gaap_AssetImpairmentCharges                                                                                                                                                                                                            | 151us-gaap_AssetImpairmentCharges                                                                                                | 8us-gaap_AssetImpairmentCharges                                                                                                                                                                                                            | 169us-gaap_AssetImpairmentCharges                                                                                                |   |   |
| Employee Severance [Member]                                                                            |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                        |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| Restructuring charges                                                                                  |                                                                                                                                                                                                                                       | 8us-gaap_RestructuringCharges/ us-gaap_RestructuringCostAndReserveAxis= us-gaap_EmployeeSeveranceMember                          |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| North America Truck [Member]                                                                           |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                        |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| Asset impairment charges                                                                               |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             | 18us-gaap_AssetImpairmentCharges/ us-gaap_StatementBusinessSegmentsAxis= nav_NorthAmericaTruckMember |   |
| Minimum [Member] | Chatham [Member] | North America Truck [Member]                                     |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                        |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
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| Maximum [Member] | Chatham [Member] | North America Truck [Member]                                     |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                        |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| Restructuring and Related Cost, Expected Cost                                                          | 60us-gaap_RestructuringAndRelatedCostExpectedCost1/ dei_EntityByLocationAxis= nav_ChathamMember/ us-gaap_RangeAxis= us-gaap_MaximumMember/ us-gaap_StatementBusinessSegmentsAxis= nav_NorthAmericaTruckMember                              |                                                                                                                             | 60us-gaap_RestructuringAndRelatedCostExpectedCost1/ dei_EntityByLocationAxis= nav_ChathamMember/ us-gaap_RangeAxis= us-gaap_MaximumMember/ us-gaap_StatementBusinessSegmentsAxis= nav_NorthAmericaTruckMember                              |                                                                                                                             |   |   |
| Maximum [Member] | Indianapolis and Waukesha Foundry [Member] | North America Truck [Member]           |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                        |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| Restructuring and Related Cost, Cost Incurred to Date                                                  | 12us-gaap_RestructuringAndRelatedCostCostIncurredToDate1/ dei_EntityByLocationAxis= nav_IndianapolisandWaukeshaFoundryMember/ us-gaap_RangeAxis= us-gaap_MaximumMember/ us-gaap_StatementBusinessSegmentsAxis= nav_NorthAmericaTruckMember |                                                                                                                             | 12us-gaap_RestructuringAndRelatedCostCostIncurredToDate1/ dei_EntityByLocationAxis= nav_IndianapolisandWaukeshaFoundryMember/ us-gaap_RangeAxis= us-gaap_MaximumMember/ us-gaap_StatementBusinessSegmentsAxis= nav_NorthAmericaTruckMember |                                                                                                                             |   | 13us-gaap_RestructuringAndRelatedCostCostIncurredToDate1/ dei_EntityByLocationAxis= nav_IndianapolisandWaukeshaFoundryMember/ us-gaap_RangeAxis= us-gaap_MaximumMember/ us-gaap_StatementBusinessSegmentsAxis= nav_NorthAmericaTruckMember |
| Brazilian Reporting Unit [Member]                                                                      |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                        |                                                                                                                                                                                                                                       |                                                                                                                             |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| Asset impairment charges                                                                               |                                                                                                                                                                                                                                       | 149us-gaap_AssetImpairmentCharges/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember                                       |                                                                                                                                                                                                                                       |                                                                                                                             |   |   |
| Goodwill, Impairment Loss                                                                              | 0us-gaap_GoodwillImpairmentLoss/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember                                                                                                                                                   | 142us-gaap_GoodwillImpairmentLoss/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember                                       | 0us-gaap_GoodwillImpairmentLoss/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember                                                                                                                                                   | 142us-gaap_GoodwillImpairmentLoss/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember                                       |   |   |
| Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)                                 | $ 0us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember                                                                                                           | $ 7us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember | $ 0us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember                                                                                                           | $ 7us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of impairment loss resulting from write-down of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit to fair value.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of costs incurred to date for the specified restructuring cost.
+ References
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| - Definition
Amount expected to be recognized in earnings for the specified restructuring cost.
+ References
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.
+ References
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