| **Financial Instruments and Commodity Contracts - Foreign Currency Contracts (Details) (Foreign Exchange Contract [Member])In Millions, unless otherwise specified**                                                                                                                                                                                                                    | Apr. 30, 2015Euro Member Countries, EuroMaturing May 2015 [Member]EUR (€)                                                                                                                                      | Apr. 30, 2015Euro Member Countries, EuroMaturing June 2015 [Member]EUR (€)                                                                                                                                      | Apr. 30, 2015Euro Member Countries, EuroMaturing July 2015 [Member]EUR (€)                                                                                                                                      | Apr. 30, 2015Euro Member Countries, EuroMaturing Aug 2015 - Oct 2015 [Member]EUR (€)                                                                                                                                              | Oct. 31, 2014Euro Member Countries, EuroMaturing Nov 2014 [Member]EUR (€) | Oct. 31, 2014Euro Member Countries, EuroMaturing Dec 2014 [Member]EUR (€)                                                                                                                                      | Oct. 31, 2014Euro Member Countries, EuroMaturing Jan 2015 [Member]EUR (€)                                                                                                                                      | Oct. 31, 2014Euro Member Countries, EuroMaturing Feb 2015 - Oct 2015 [Member]EUR (€)                                                                                                                           | Apr. 30, 2015Canada, DollarsMaturing May 2015 [Member]CAD                                                                                                                                                                                | Apr. 30, 2015Canada, DollarsMaturing June 2015 [Member]CAD | Apr. 30, 2015Canada, DollarsMaturing July 2015 [Member]CAD                                                                                                                                                    | Apr. 30, 2015Canada, DollarsMaturing Aug 2015 - Oct 2015 [Member]CAD                                                                                                                                           |
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| **Derivative [Line Items]**                                                                                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                  |                                                                                                                                                                                                                   |                                                                                                                                                                                                                   |                                                                                                                                                                                                                                     |                                                                                  |                                                                                                                                                                                                                  |                                                                                                                                                                                                                  |                                                                                                                                                                                                                  |                                                                                                                                                                                                                                     |                                                            |                                                                                                                                                                                                          |                                                                                                                                                                                                           |   |   |  |
| Derivative, Notional Amount Expiring Monthly                                                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                  |                                                                                                                                                                                                                   |                                                                                                                                                                                                                   | € 2nav_DerivativeNotionalAmountExpiringMonthly/ us-gaap_CurrencyAxis= currency_EUR/ us-gaap_DerivativeByNatureAxis= nav_MaturingAug2015Oct2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember |                                                                                  |                                                                                                                                                                                                                  |                                                                                                                                                                                                                  |                                                                                                                                                                                                                  | € 1nav_DerivativeNotionalAmountExpiringMonthly/ us-gaap_CurrencyAxis= currency_EUR/ us-gaap_DerivativeByNatureAxis= nav_MaturingFeb2015Oct2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember |                                                            |                                                                                                                                                                                                          |                                                                                                                                                                                                           |   | 25nav_DerivativeNotionalAmountExpiringMonthly/ us-gaap_CurrencyAxis= currency_CAD/ us-gaap_DerivativeByNatureAxis= nav_MaturingAug2015Oct2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember |  |
| Derivative, Notional Amount                                                                                                                                                                                                                                                                                                                                                             | € 6invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_EUR/ us-gaap_DerivativeByNatureAxis= nav_MaturingMay2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember | € 5invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_EUR/ us-gaap_DerivativeByNatureAxis= nav_MaturingJune2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember | € 5invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_EUR/ us-gaap_DerivativeByNatureAxis= nav_MaturingJuly2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember | € 6invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_EUR/ us-gaap_DerivativeByNatureAxis= nav_MaturingAug2015Oct2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember             | [1]                                                                              | € 4invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_EUR/ us-gaap_DerivativeByNatureAxis= nav_MaturingNov2014Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember | € 4invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_EUR/ us-gaap_DerivativeByNatureAxis= nav_MaturingDec2014Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember | € 5invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_EUR/ us-gaap_DerivativeByNatureAxis= nav_MaturingJan2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember | € 9invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_EUR/ us-gaap_DerivativeByNatureAxis= nav_MaturingFeb2015Oct2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember             | [2]                                                        | 25invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_CAD/ us-gaap_DerivativeByNatureAxis= nav_MaturingMay2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember | 25invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_CAD/ us-gaap_DerivativeByNatureAxis= nav_MaturingJune2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember | 25invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_CAD/ us-gaap_DerivativeByNatureAxis= nav_MaturingJuly2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember | 75invest_DerivativeNotionalAmount/ us-gaap_CurrencyAxis= currency_CAD/ us-gaap_DerivativeByNatureAxis= nav_MaturingAug2015Oct2015Member/ us-gaap_DerivativeInstrumentRiskAxis= us-gaap_ForeignExchangeContractMember | [3] |
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| [1]Forward exchange contracts of €2 million expire on the last day of each month from August 2015 through October 2015.[2]Forward exchange contracts of €1 million expire on the last day of each month from February 2015 through October 2015.[3]Forward exchange contracts of C$25 million expire on the last day of each month from August 2015 through October 2015. |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B
+ Details**Name:**invest_DerivativeNotionalAmount**Namespace Prefix:**invest_**Data Type:**xbrli:monetaryItemType**Balance Type:**na**Period Type:**instant |
| X                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Derivative, Notional Amount Expiring Monthly
+ References
No definition available.
+ Details**Name:**nav_DerivativeNotionalAmountExpiringMonthly**Namespace Prefix:**nav_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_DerivativeLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |