| **Restructuring and Impairments - Schedule of Impairment Charges (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]**                                                                             |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| Other Asset Impairment Charges                                                                                              | $ 1us-gaap_OtherAssetImpairmentCharges                                                                                         | $ 2us-gaap_OtherAssetImpairmentCharges                                                                                         | $ 8us-gaap_OtherAssetImpairmentCharges                                                                                         | $ 20us-gaap_OtherAssetImpairmentCharges |   |
| Asset impairment charges                                                                                                    | 1us-gaap_AssetImpairmentCharges                                                                                                | 151us-gaap_AssetImpairmentCharges                                                                                              | 8us-gaap_AssetImpairmentCharges                                                                                                | 169us-gaap_AssetImpairmentCharges |   |
| Brazilian Reporting Unit [Member]                                                                                           |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| **Restructuring Cost and Reserve [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 |   |
| 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 |   |
| Asset impairment charges                                                                                                    |                                                                                                                           | 149us-gaap_AssetImpairmentCharges/ nav_ReportingUnitAxis= nav_BrazilianReportingUnitMember                                     |                                                                                                                           |   |   |
| Impairment charges [Member]                                                                                                 |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                                             |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| Asset impairment charges                                                                                                    |                                                                                                                           |                                                                                                                           |                                                                                                                           | 169us-gaap_AssetImpairmentCharges/ nav_ImpairmentTypeAxis= nav_ImpairmentchargesMember |   |
| North America Truck [Member]                                                                                                |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                                                             |                                                                                                                           |                                                                                                                           |                                                                                                                           |   |   |
| Asset impairment charges                                                                                                    |                                                                                                                           |                                                                                                                           |                                                                                                                           |   | $ 18us-gaap_AssetImpairmentCharges/ us-gaap_StatementBusinessSegmentsAxis= nav_NorthAmericaTruckMember |

| 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
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=d3e3602-108585Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=8077374&loc=d3e2420-110228
+ Details**Name:**us-gaap_AssetImpairmentCharges**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| 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
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=d3e3602-108585Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13777-109266Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267
+ Details**Name:**us-gaap_GoodwillImpairmentLoss**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| 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
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16373-109275
+ Details**Name:**us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The charge against earnings resulting from the write down of long lived assets other than goodwill due to the difference between the carrying value and lower fair value.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2921-110230
+ Details**Name:**us-gaap_OtherAssetImpairmentCharges**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RestructuringCostAndReserveLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                          |
|--------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**nav_ImpairmentTypeAxis=nav_ImpairmentchargesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**nav_ReportingUnitAxis=nav_BrazilianReportingUnitMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_StatementBusinessSegmentsAxis=nav_NorthAmericaTruckMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |