| **Finance Receivables - Narrative (Details) (USD $)**                  | Apr. 30, 2015segments                                                                                                                       | Jan. 31, 2015segments                               | Oct. 31, 2014                                                                                                                             |
|------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------|
| **Schedule of Securitization [Line Items]**                            |                                                                                                                                        |                                                |                                                                                                                                      |
| Loans and Leases Receivable, Net Amount                                | $ 2,200,000,000us-gaap_LoansAndLeasesReceivableNetReportedAmount                                                                            |                                                | $ 2,000,000,000us-gaap_LoansAndLeasesReceivableNetReportedAmount                                                                          |
| Number of Portfolio Segments for Finance Receivables                   | 2nav_NumberofPortfolioSegmentsforFinanceReceivables                                                                                         | 2nav_NumberofPortfolioSegmentsforFinanceReceivables |                                                                                                                                      |
| Trac Funding Facility [Member]                                         |                                                                                                                                        |                                                |                                                                                                                                      |
| **Schedule of Securitization [Line Items]**                            |                                                                                                                                        |                                                |                                                                                                                                      |
| Finance Receivables Retail Accounts Collateral For Borrowed Securities | 1,100,000,000nav_FinanceReceivablesRetailAccountsCollateralForBorrowedSecurities/ us-gaap_DebtInstrumentAxis= nav_TracFundingFacilityMember |                                                | 996,000,000nav_FinanceReceivablesRetailAccountsCollateralForBorrowedSecurities/ us-gaap_DebtInstrumentAxis= nav_TracFundingFacilityMember |
| Cash Collateral for Borrowed Securities                                | 149,000,000us-gaap_CashCollateralForBorrowedSecurities/ us-gaap_DebtInstrumentAxis= nav_TracFundingFacilityMember                           |                                                | 93,000,000us-gaap_CashCollateralForBorrowedSecurities/ us-gaap_DebtInstrumentAxis= nav_TracFundingFacilityMember                          |
| Financial Services Operations [Member]                                 |                                                                                                                                        |                                                |                                                                                                                                      |
| **Schedule of Securitization [Line Items]**                            |                                                                                                                                        |                                                |                                                                                                                                      |
| Assets Net Of Intercompany Balances                                    | $ 2,600,000,000nav_AssetsNetOfIntercompanyBalances/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember            |                                                | $ 2,600,000,000nav_AssetsNetOfIntercompanyBalances/ us-gaap_StatementBusinessSegmentsAxis= nav_FinancialServicesOperationsMember          |

| X                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Assets Net Of Intercompany Balances
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| X                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Finance Receivables Retail Accounts Collateral For Borrowed Securities
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| X                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of Portfolio Segments for Finance Receivables
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying amount as of the balance sheet date of cash collateral held for borrowed securities, for which the cash is restricted as to withdrawal or usage.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.
+ References
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| X                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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