| **Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions**                        | 3 Months Ended | 12 Months Ended |        |
|--------------------------------------------------------------------------------------------------|----------------|-----------------|--------|
||
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]** |           |            |   |   |   |   |   |   |   |   |   |
| Goodwill, Impairment Loss                                                                        |           |            |   |   |   |   |   | $ 0 | $ 142 | $ 81 |   |
| Indefinite-Lived Intangible Assets (Excluding Goodwill)                                          | $ 19           |            |   |   |   |   |   | 19 | 34 |   |   |
| Asset impairment charges                                                                         |           |            |   |   |   |   |   | 30 | 183 | 97 |   |
| Goodwill                                                                                         | 38             |            |   |   |   | $ 184 |   | $ 38 | 38 | 184 | $ 280 |
| 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                                                                        |           |            |   |   |   |   |   | $ 0 | 142 | 81 |   |
| Indefinite-Lived Intangible Assets (Excluding Goodwill)                                          |           | $ 24            |   | $ 43 |   |   |   |   |   |   |   |
| Asset impairment charges                                                                         |           |            |   | 149 |   |   |   |   |   |   |   |
| Goodwill                                                                                         |           |            |   | 142 |   |   |   |   |   |   |   |
| Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)                           |           | 3               |   | $ 7 |   |   |   | 7 | 7 | 0 |   |
| North America Truck [Member]                                                                     |           |            |   |   |   |   |   |   |   |   |   |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]** |           |            |   |   |   |   |   |   |   |   |   |
| Goodwill, Impairment Loss                                                                        |           |            |   |   |   | 77 | $ 4 | 0 | 0 | 81 |   |
| Asset impairment charges                                                                         |           |            |   |   | $ 19 |   |   |   | 33 |   |   |
| Goodwill                                                                                         | 0              |            |   |   |   | $ 0 |   | $ 0 | $ 0 | $ 0 | $ 82 |
| Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)                           | $ 4            | $ 3             | $ 7    |   |   |   |   |   |   |   |   |

| X                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Maximum maturity term for a cash and cash equivalent instrument
+ References
No definition available.
+ Details**Name:**nav_CashandCashEquivalentsMaturityTerm**Namespace Prefix:**nav_**Data Type:**xbrli:durationItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Maximum maturity term for a marketable security instrument
+ References
No definition available.
+ Details**Name:**nav_MarketableSecuritiesMaturityTerm**Namespace Prefix:**nav_**Data Type:**xbrli:durationItemType**Balance Type:**na**Period Type:**duration |
| 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=8077374&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=31042434&loc=d3e3602-108585
+ Details**Name:**us-gaap_AssetImpairmentCharges**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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**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 -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=d3e13770-109266
+ Details**Name:**us-gaap_Goodwill**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| 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 350 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13854-109267Reference 2: 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 3: 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 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
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=26713463&loc=d3e16323-109275
+ Details**Name:**us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| 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:** |