| **Stock-based Compensation Plans - Schedule of Stock Based Compensation Other than Options (Details) (USD $)In Thousands, except Per Share data, unless otherwise specified** | 12 Months Ended                                                                                                                                                                                                                                                                               |
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| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]**    |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                                               | $ 14.12us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue                                                                                                                                      | $ 14.01us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue |   |
| Performance-based Stock Unit [Member]                                                                                                                                         |                                                                                                                                                                                                                                                                                          |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]**                      |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 326us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember                                                                                                              | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember |   |
| Equity Instruments Other than Options, Grants in Period                                                                                                                       | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember                                                                                                                 | 381us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember |   |
| Equity Instruments Other than Options, Vested in Period                                                                                                                       | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember                                                                                                                 | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember |   |
| Equity Instruments Other than Options, Forfeited in Period                                                                                                                    | 34us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember                                                                                                             | 55us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 292us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember                                                                                                              | 326us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]**    |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 28.35us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember                                                                               | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember |   |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                                               | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember                                                                           | $ 28.19us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember |   |
| Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value                                                                               | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember                                                                           | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember |   |
| Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value                                                                                    | $ 27.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember                                                                             | $ 27.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 28.48us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember                                                                               | $ 28.35us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockUnitMember |   |
| Market-based Stock Options [Member] [Member]                                                                                                                                  |                                                                                                                                                                                                                                                                                          |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]**                      |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 759us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                                                          | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Equity Instruments Other than Options, Grants in Period                                                                                                                       | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                                                             | 917us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Equity Instruments Other than Options, Vested in Period                                                                                                                       | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                                                             | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Equity Instruments Other than Options, Forfeited in Period                                                                                                                    | 89us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                                                         | 158us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 670us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                                                          | 759us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Equity Instruments Other Than Options, Exercisable, Number                                                                                                                    | 0nav_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisableNumber/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                                                              | 0nav_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisableNumber/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]**    |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 27.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                           | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                                               | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                       | $ 27.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value                                                                               | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                       | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value                                                                                    | $ 27.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                         | $ 27.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 27.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                           | $ 27.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Equity Instruments Other Than Options, Exercisable, Weighted Average Exercise Price                                                                                           | $ 0.00nav_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisableWeightedAverageExercisePrice/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember                                                                                   | $ 0.00nav_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisableWeightedAverageExercisePrice/ us-gaap_AwardTypeAxis= nav_MarketbasedStockOptionsMemberMember |   |
| Share-Settled Restricted Stock Units [Member]                                                                                                                                 |                                                                                                                                                                                                                                                                                          |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]**                      |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 299us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember                                                                                                       | 77us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember | 162us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Grants in Period                                                                                                                       | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember                                                                                                          | 316us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember | 6us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Vested in Period                                                                                                                       | 90us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember                                                                                                         | 26us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember | 90us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Forfeited in Period                                                                                                                    | 21us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember                                                                                                      | 68us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember | 1us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 188us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember                                                                                                       | 299us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember | 77us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]**    |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 29.54us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember                                                                        | $ 45.93us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember | $ 35.54us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                                               | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember                                                                    | $ 28.13us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember | $ 42.19us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value                                                                               | $ 31.74us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember                                                                   | $ 35.84us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember | $ 27.22us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value                                                                                    | $ 27.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember                                                                      | $ 39.13us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember | $ 33.97us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 28.75us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember                                                                        | $ 29.54us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember | $ 45.93us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_ShareSettledRestrictedStockUnitsMember |
| Performance-based Stock Options [Member]                                                                                                                                      |                                                                                                                                                                                                                                                                                          |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]**                      |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 299us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                                                           | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Equity Instruments Other than Options, Grants in Period                                                                                                                       | 651us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                                                            | 299us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Equity Instruments Other than Options, Vested in Period                                                                                                                       | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                                                              | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Equity Instruments Other than Options, Forfeited in Period                                                                                                                    | 9us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                                                           | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 941us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                                                           | 299us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Equity Instruments Other Than Options, Exercisable, Number                                                                                                                    | 0nav_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisableNumber/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                                                               | 0nav_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisableNumber/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]**    |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 34.47us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                            | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                                               | $ 35.83us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                       | $ 34.47us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value                                                                               | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                        | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value                                                                                    | $ 35.09us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                          | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 35.41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                            | $ 34.47us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Equity Instruments Other Than Options, Exercisable, Weighted Average Exercise Price                                                                                           | $ 0.00nav_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisableWeightedAverageExercisePrice/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember                                                                                    | $ 0.00nav_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisableWeightedAverageExercisePrice/ us-gaap_AwardTypeAxis= nav_PerformancebasedStockOptionsMember |   |
| Restricted Stock [Member]                                                                                                                                                     |                                                                                                                                                                                                                                                                                          |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]**                      |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                                                     | 41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Equity Instruments Other than Options, Grants in Period                                                                                                                       | 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                                                       | 2us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | 44us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Equity Instruments Other than Options, Vested in Period                                                                                                                       | 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                                                       | 2us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Equity Instruments Other than Options, Forfeited in Period                                                                                                                    | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                                                    | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                                                     | 41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | 41us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]**    |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 24.13us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                     | $ 24.13us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                                               | $ 33.70us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                | $ 34.19us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | $ 25.06us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value                                                                               | $ 33.70us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                | $ 34.19us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | $ 40.76us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value                                                                                    | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                    | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 24.13us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember                                                                                     | $ 24.13us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember | $ 24.13us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= us-gaap_RestrictedStockMember |
| Cash-Settled Restricted Stock Units [Member]                                                                                                                                  |                                                                                                                                                                                                                                                                                          |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]**                      |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 194us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember                                                                                                        | 463us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember | 393us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Grants in Period                                                                                                                       | 470us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember                                                                                                         | 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember | 285us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Vested in Period                                                                                                                       | 124us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember                                                                                                         | 215us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember | 158us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Forfeited in Period                                                                                                                    | 71us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember                                                                                                       | 57us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember | 57us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 469us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember                                                                                                        | 194us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember | 463us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]**    |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 43.74us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember                                                                         | $ 43.20us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember | $ 48.80us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                                               | $ 32.44us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember                                                                    | $ 27.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember | $ 37.10us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value                                                                               | $ 47.48us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember                                                                    | $ 42.71us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember | $ 46.18us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value                                                                                    | $ 33.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember                                                                       | $ 42.46us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember | $ 43.58us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 33.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember                                                                         | $ 43.74us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember | $ 43.20us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ us-gaap_AwardTypeAxis= nav_CashSettledRestrictedStockUnitsMember |
| Service and Market Measures [Member] | Cash-settled Performance-based Stock Unit [Member]                                                                                     |                                                                                                                                                                                                                                                                                          |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]**                      |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 172us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember                                          | 314us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember | 161us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |
| Equity Instruments Other than Options, Grants in Period                                                                                                                       | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember                                             | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember | 153us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |
| Equity Instruments Other than Options, Vested in Period                                                                                                                       | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember                                             | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |
| Equity Instruments Other than Options, Forfeited in Period                                                                                                                    | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember                                          | 142us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 172us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember                                          | 172us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember | 314us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]**    |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 69.64us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember           | $ 68.03us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember | $ 84.75us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                                               | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember       | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember | $ 50.52us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |
| Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value                                                                               | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember       | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |
| Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value                                                                                    | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember          | $ 66.09us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 69.64us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember           | $ 69.64us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember | $ 68.03us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandMarketMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |
| Service and Performance Measures [Member] | Cash-settled Performance-based Stock Unit [Member]                                                                                |                                                                                                                                                                                                                                                                                          |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]**                      |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ nav_AwardMetricAxis= nav_ServiceandPerformanceMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember                                       |   |   |
| Equity Instruments Other than Options, Grants in Period                                                                                                                       | 225us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod/ nav_AwardMetricAxis= nav_ServiceandPerformanceMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember                                      |   |   |
| Equity Instruments Other than Options, Vested in Period                                                                                                                       | 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod/ nav_AwardMetricAxis= nav_ServiceandPerformanceMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember                                        |   |   |
| Equity Instruments Other than Options, Forfeited in Period                                                                                                                    | 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod/ nav_AwardMetricAxis= nav_ServiceandPerformanceMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember                                     |   |   |
| Equity Instruments Other than Options, Nonvested, Number                                                                                                                      | 221us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber/ nav_AwardMetricAxis= nav_ServiceandPerformanceMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember                                     |   |   |
| **Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]**    |                                                                                                                                                                                                                                                                                          |   |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandPerformanceMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember       |   |   |
| Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value                                                                               | $ 35.10us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandPerformanceMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember |   |   |
| Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value                                                                               | $ 0.00us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandPerformanceMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember  |   |   |
| Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value                                                                                    | $ 35.09us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandPerformanceMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember    |   |   |
| Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value                                                                                      | $ 35.11us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue/ nav_AwardMetricAxis= nav_ServiceandPerformanceMeasuresMember/ us-gaap_AwardTypeAxis= nav_CashsettledPerformancebasedStockUnitMember      |   |   |

| X                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other Than Options, Exercisable, Number
+ References
No definition available.
+ Details**Name:**nav_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisableNumber**Namespace Prefix:**nav_**Data Type:**xbrli:sharesItemType**Balance Type:**na**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other Than Options, Exercisable, Weighted Average Exercise Price
+ References
No definition available.
+ Details**Name:**nav_SharebasedCompensationArrangementbySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisableWeightedAverageExercisePrice**Namespace Prefix:**nav_**Data Type:**num:perShareItemType**Balance Type:**na**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
+ Details**Name:**us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue**Namespace Prefix:**us-gaap_**Data Type:**num:perShareItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
+ Details**Name:**us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod**Namespace Prefix:**us-gaap_**Data Type:**xbrli:sharesItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
+ Details**Name:**us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue**Namespace Prefix:**us-gaap_**Data Type:**num:perShareItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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| X                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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| X                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901
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| X                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**nav_AwardMetricAxis=nav_ServiceandPerformanceMeasuresMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_AwardTypeAxis=nav_PerformancebasedStockUnitMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------|
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