| **Fair Value Measurements - Narrative (Details) (USD $)In Millions, unless otherwise specified** | 3 Months Ended                                                                                                                 | 6 Months Ended                                                                                                                 | 3 Months Ended                                                                                                                 |                                                                                                                                |
|--------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------|
||
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]** |                                                                                                                           |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| Asset impairment charges                                                                         | $ 1us-gaap_AssetImpairmentCharges                                                                                              | $ 151us-gaap_AssetImpairmentCharges                                                                                            | $ 8us-gaap_AssetImpairmentCharges                                                                                              | $ 169us-gaap_AssetImpairmentCharges                                                                                            |   |   |
| Goodwill                                                                                         | 38us-gaap_Goodwill                                                                                                             |                                                                                                                           | 38us-gaap_Goodwill                                                                                                             |                                                                                                                           |   | 38us-gaap_Goodwill |
| Cash and Cash Equivalents, Maturity Term                                                         |                                                                                                                           |                                                                                                                           | 90 days                                                                                                                        |                                                                                                                           |   |   |
| Marketable Securities, Maturity Term                                                             |                                                                                                                           |                                                                                                                           | 90 days                                                                                                                        |                                                                                                                           |   |   |
| Brazilian Reporting Unit [Member]                                                                |                                                                                                                           |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]** |                                                                                                                           |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| 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                                     |   |   |
| Indefinite-Lived Intangible Assets (Excluding Goodwill)                                          |                                                                                                                           | 43us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember            |                                                                                                                           | 43us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember            |   |   |
| Asset impairment charges                                                                         |                                                                                                                           | 149us-gaap_AssetImpairmentCharges/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember                                     |                                                                                                                           |                                                                                                                           |   |   |
| Goodwill                                                                                         |                                                                                                                           | 142us-gaap_Goodwill/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember                                                   |                                                                                                                           | 142us-gaap_Goodwill/ 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 |   |   |
| North America Truck [Member]                                                                     |                                                                                                                           |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]** |                                                                                                                           |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| Asset impairment charges                                                                         |                                                                                                                           |                                                                                                                           |                                                                                                                           |                                                                                                                           | $ 18us-gaap_AssetImpairmentCharges/ us-gaap_StatementBusinessSegmentsAxis= nav_NorthAmericaTruckMember |   |

| X                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Maximum maturity term for a cash and cash equivalent instrument
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Maximum maturity term for a marketable security instrument
+ References
No definition available.
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| 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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| X                                                                                                                                                                                                                 |
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount after accumulated impairment loss of an asset representing 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 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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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.
+ References
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| X                                                                                                                                              |
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