| **Restructuring and Impairments - Narrative (Details) - USD ($) $ in Millions**           | 3 Months Ended | 9 Months Ended |        |
|-------------------------------------------------------------------------------------------|----------------|----------------|--------|
||
| **Restructuring Cost and Reserve [Line Items]**                                           |           |           |   |   |   |   |   |
| Restructuring charges                                                                     | $ 5            | $ 13           |   |   | $ 11 | $ 22 |   |
| Restructuring and Related Cost, Incurred Cost                                             |           |           |   |   | 4 | 19 |   |
| Asset impairment charges                                                                  | 12             | 7              |   |   | 17 | 15 |   |
| Goodwill                                                                                  | 38             |           |   |   | 38 |   | $ 38 |
| Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)                    | 1              | 3              |   |   | 1 | 3 |   |
| Other Restructuring [Member]                                                              |           |           |   |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                           |           |           |   |   |   |   |   |
| Restructuring and Related Cost, Incurred Cost                                             |           |           |   |   | 0 | 2 |   |
| Employee Severance [Member]                                                               |           |           |   |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                           |           |           |   |   |   |   |   |
| Restructuring charges                                                                     |           | 13             |   |   |   |   |   |
| Restructuring and Related Cost, Incurred Cost                                             |           |           |   |   | 4 | 17 |   |
| Lease Vacancy [Member] [Domain]                                                           |           |           |   |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                           |           |           |   |   |   |   |   |
| Restructuring and Related Cost, Incurred Cost                                             |           |           |   |   | 0 | 0 |   |
| North America Truck [Member]                                                              |           |           |   |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                           |           |           |   |   |   |   |   |
| Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)                    | 11             |           | $ 7    |   |   |   |   |
| Indianapolis and Waukesha Foundry [Member] | North America Truck [Member]                 |           |           |   |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                           |           |           |   |   |   |   |   |
| Restructuring and Related Cost, Incurred Cost                                             |           | 3              |   |   |   | 28 |   |
| Minimum [Member] | Chatham [Member] | North America Truck [Member]                        |           |           |   |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                           |           |           |   |   |   |   |   |
| Restructuring and Related Cost, Expected Cost                                             | 0              |           |   |   | 0 |   |   |
| Maximum [Member] | Chatham [Member] | North America Truck [Member]                        |           |           |   |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                           |           |           |   |   |   |   |   |
| Restructuring and Related Cost, Expected Cost                                             | 60             |           |   |   | $ 60 |   |   |
| Brazilian Reporting Unit [Member]                                                         |           |           |   |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                           |           |           |   |   |   |   |   |
| Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)                    | 1              | 3              |   |   |   |   |   |
| Indefinite-Lived Intangible Assets (Excluding Goodwill)                                   |           | $ 24           |   |   |   | $ 24 |   |
| Other Postretirement Benefit Plan [Member] | Chatham [Member] | Facility Closing [Member] |           |           |   |   |   |   |   |
| **Restructuring Cost and Reserve [Line Items]**                                           |           |           |   |   |   |   |   |
| Postemployment Benefits, Period Expense                                                   | $ 5            |           |   | $ 14 |   |   |   |

| 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 360 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228Reference 2: 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=66902209&loc=d3e3602-108585
+ Details**Name:**us-gaap_AssetImpairmentCharges**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| 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
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=64834752&loc=SL49117168-202975
+ Details**Name:**us-gaap_Goodwill**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| 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=66006027&loc=d3e16373-109275
+ Details**Name:**us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275
+ Details**Name:**us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Period expense related to postemployment benefits.
+ References
No definition available.
+ Details**Name:**us-gaap_PostemploymentBenefitsPeriodExpense**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount expected to be recognized in earnings for the specified 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=d3e140904-122747
+ Details**Name:**us-gaap_RestructuringAndRelatedCostExpectedCost1**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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=d3e140904-122747
+ Details**Name:**us-gaap_RestructuringAndRelatedCostIncurredCost**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 5.P.3) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140864-122747Reference 2: 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=66902209&loc=d3e3602-108585Reference 3: 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 4: 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=d3e140904-122747
+ Details**Name:**us-gaap_RestructuringCharges**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
+ Details**Name:**us-gaap_RestructuringCostAndReserveLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RestructuringCostAndReserveAxis=us-gaap_OtherRestructuringMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RestructuringCostAndReserveAxis=us-gaap_EmployeeSeveranceMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RestructuringCostAndReserveAxis=nav_LeaseVacancyMemberDomain**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:** |
| X                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**dei_EntityByLocationAxis=nav_IndianapolisandWaukeshaFoundryMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RangeAxis=us-gaap_MinimumMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**dei_EntityByLocationAxis=nav_ChathamMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RangeAxis=us-gaap_MaximumMember**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_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RestructuringCostAndReserveAxis=us-gaap_FacilityClosingMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |