| **Segment Reporting - Narrative (Details) $ in Millions** | 3 Months Ended | 9 Months Ended |
|-----------------------------------------------------------|----------------|----------------|
||
| **Segment Reporting Information [Line Items]**            |           |           |   |   |
| Number Of Segments | segments                             | 4              |           |   |   |
| Intersegment sales and revenues                           | $ 0            | $ 0            | $ 0 | $ 0 |
| Sales and revenues, net                                   | 2,086          | 2,538          | 6,048 | 7,652 |
| North America Truck [Member]                              |           |           |   |   |
| **Segment Reporting Information [Line Items]**            |           |           |   |   |
| Intersegment sales and revenues                           | 9              | 49             | 81 | 121 |
| Sales and revenues, net                                   | 1,395          | 1,834          | 4,007 | 5,470 |
| North America Parts [Member]                              |           |           |   |   |
| **Segment Reporting Information [Line Items]**            |           |           |   |   |
| Intersegment sales and revenues                           | 8              | 11             | 23 | 29 |
| Sales and revenues, net                                   | 597            | 625            | 1,814 | 1,864 |
| Corporate And Eliminations [Member]                       |           |           |   |   |
| **Segment Reporting Information [Line Items]**            |           |           |   |   |
| Intersegment sales and revenues                           | (55)           | (95)           | (212) | (263) |
| Sales and revenues, net                                   | $ (51)         | $ (93)         | $ (204) | $ (256) |

| X                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Intersegment sales and revenues
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.
+ References
No definition available.
+ Details**Name:**us-gaap_NumberOfReportableSegments**Namespace Prefix:**us-gaap_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688
+ Details**Name:**us-gaap_Revenues**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**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_SegmentReportingInformationLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_StatementBusinessSegmentsAxis=nav_NorthAmericaTruckMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_StatementBusinessSegmentsAxis=nav_NorthAmericaPartsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_StatementBusinessSegmentsAxis=nav_CorporateAndEliminationsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |