| **Segment Reporting - Summary of Segment Long Lived Assets and Revenue (Details) (USD $)In Millions, unless otherwise specified** | 3 Months Ended                                                                                                   | 6 Months Ended                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------|
||
| **Revenues from External Customers and Long-Lived Assets [Line Items]**                                                           |                                                                                                             |                                                                                                             |   |   |
| Sales and revenues, net                                                                                                           | $ 2,693us-gaap_Revenues                                                                                          | $ 2,746us-gaap_Revenues                                                                                          | $ 5,114us-gaap_Revenues | $ 4,954us-gaap_Revenues |
| Financial Services Operations [Member]                                                                                            |                                                                                                             |                                                                                                             |   |   |
| **Revenues from External Customers and Long-Lived Assets [Line Items]**                                                           |                                                                                                             |                                                                                                             |   |   |
| Investment Income, Interest                                                                                                       | 44us-gaap_InvestmentIncomeInterest/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember | 42us-gaap_InvestmentIncomeInterest/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember | 89us-gaap_InvestmentIncomeInterest/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember | 82us-gaap_InvestmentIncomeInterest/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember |
| Sales and revenues, net                                                                                                           | $ 60us-gaap_Revenues/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember               | $ 57us-gaap_Revenues/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember               | $ 120us-gaap_Revenues/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember | $ 112us-gaap_Revenues/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Article 5Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(b)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688
+ Details**Name:**us-gaap_InvestmentIncomeInterest**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**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=26872669&loc=d3e20235-122688Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5
+ Details**Name:**us-gaap_Revenues**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_StatementBusinessSegmentsAxis=nav_FinancialServicesOperationsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |