| **Income Taxes - Narrative (Details) (USD $)In Millions, unless otherwise specified**                     | 3 Months Ended                                                                                                                | 12 Months Ended                                                                                              |
|-----------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------|
||
| **Operating Loss Carryforwards [Line Items]**                                                             |                                                                                                                          |                                                                                                         |   |   |   |
| Unrecognized Tax Benefits that Would Not Impact Effective Tax Rate                                        | $ 4nav_UnrecognizedTaxBenefitsThatWouldNotImpactEffectiveTaxRate                                                              |                                                                                                         | $ 4nav_UnrecognizedTaxBenefitsThatWouldNotImpactEffectiveTaxRate |   |   |
| Deferred Tax Assets, Operating Loss Carryforwards, Domestic                                               | 870us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic                                                                |                                                                                                         | 870us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsDomestic |   |   |
| Income Tax Expense (Benefit)                                                                              |                                                                                                                          |                                                                                                         | 26us-gaap_IncomeTaxExpenseBenefit | (171)us-gaap_IncomeTaxExpenseBenefit | 1,780us-gaap_IncomeTaxExpenseBenefit |
| Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount                                      | (16)us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount                                                                  | 29us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount                                                   | 234us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount | 350us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount | 2,200us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount |
| Undistributed Earnings of Foreign Subsidiaries                                                            | 469us-gaap_UndistributedEarningsOfForeignSubsidiaries                                                                         |                                                                                                         | 469us-gaap_UndistributedEarningsOfForeignSubsidiaries |   |   |
| Deferred Tax Assets, Operating Loss Carryforwards, State and Local                                        | 144us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal                                                           |                                                                                                         | 144us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal |   |   |
| Deferred Tax Assets, Operating Loss Carryforwards, Foreign                                                | 199us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsForeign                                                                 |                                                                                                         | 199us-gaap_DeferredTaxAssetsOperatingLossCarryforwardsForeign |   |   |
| Deferred Tax Assets, Operating Loss Carryforwards                                                         | 1,213us-gaap_DeferredTaxAssetsOperatingLossCarryforwards                                                                      |                                                                                                         | 1,213us-gaap_DeferredTaxAssetsOperatingLossCarryforwards | 840us-gaap_DeferredTaxAssetsOperatingLossCarryforwards |   |
| Deferred Tax Assets, Valuation Allowance                                                                  | 3,174us-gaap_DeferredTaxAssetsValuationAllowance                                                                              |                                                                                                         | 3,174us-gaap_DeferredTaxAssetsValuationAllowance | 2,773us-gaap_DeferredTaxAssetsValuationAllowance |   |
| Income Taxes Percent Likelihood Of Being Realized Upon Settlement                                         | 50.00%nav_IncomeTaxesPercentLikelihoodOfBeingRealizedUponSettlement                                                           |                                                                                                         | 50.00%nav_IncomeTaxesPercentLikelihoodOfBeingRealizedUponSettlement |   |   |
| Unrecognized Tax Benefits                                                                                 | 47us-gaap_UnrecognizedTaxBenefits                                                                                             |                                                                                                         | 47us-gaap_UnrecognizedTaxBenefits | 88us-gaap_UnrecognizedTaxBenefits |   |
| offsetting tax benefits associated with the correlative effects of potential transfer pricing adjustments | 12nav_OffsettingTaxBenefitsAssociatedWithCorrelativeEffectsOfPotentialTransferPricingAdjustments                              |                                                                                                         | 12nav_OffsettingTaxBenefitsAssociatedWithCorrelativeEffectsOfPotentialTransferPricingAdjustments |   |   |
| Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense                                      |                                                                                                                          |                                                                                                         |   | 6us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense | 11us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense |
| Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued                                      | 8us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued                                                          |                                                                                                         | 8us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued | 12us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued |   |
| Liability for Uncertain Tax Benefits Time Range                                                           |                                                                                                                          |                                                                                                         | 12 days |   |   |
| Intraperiod Tax Allocation Rule [Member]                                                                  |                                                                                                                          |                                                                                                         |   |   |   |
| **Operating Loss Carryforwards [Line Items]**                                                             |                                                                                                                          |                                                                                                         |   |   |   |
| Income Tax Expense (Benefit)                                                                              |                                                                                                                          |                                                                                                         |   | (220)us-gaap_IncomeTaxExpenseBenefit/ us-gaap_IncomeTaxAuthorityAxis= nav_IntraperiodTaxAllocationRuleMember |   |
| Domestic Tax Authority [Member]                                                                           |                                                                                                                          |                                                                                                         |   |   |   |
| **Operating Loss Carryforwards [Line Items]**                                                             |                                                                                                                          |                                                                                                         |   |   |   |
| Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount                                      |                                                                                                                          |                                                                                                         |   |   | (189)us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount/ us-gaap_IncomeTaxAuthorityAxis= us-gaap_DomesticCountryMember |
| Other Comprehensive Income (Loss) [Member]                                                                |                                                                                                                          |                                                                                                         |   |   |   |
| **Operating Loss Carryforwards [Line Items]**                                                             |                                                                                                                          |                                                                                                         |   |   |   |
| Income Tax Expense (Benefit)                                                                              |                                                                                                                          |                                                                                                         |   | (212)us-gaap_IncomeTaxExpenseBenefit/ us-gaap_InformationByFinancialStatementLineItemAxis= us-gaap_OtherComprehensiveIncomeMember |   |
| Additional Paid-in Capital [Member]                                                                       |                                                                                                                          |                                                                                                         |   |   |   |
| **Operating Loss Carryforwards [Line Items]**                                                             |                                                                                                                          |                                                                                                         |   |   |   |
| Income Tax Expense (Benefit)                                                                              |                                                                                                                          |                                                                                                         |   | (8)us-gaap_IncomeTaxExpenseBenefit/ us-gaap_InformationByFinancialStatementLineItemAxis= us-gaap_AdditionalPaidInCapitalMember |   |
| Convertible Subordinated Debt [Member]                                                                    |                                                                                                                          |                                                                                                         |   |   |   |
| **Operating Loss Carryforwards [Line Items]**                                                             |                                                                                                                          |                                                                                                         |   |   |   |
| Income Tax Expense (Benefit)                                                                              |                                                                                                                          | (13)us-gaap_IncomeTaxExpenseBenefit/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember |   |   |   |
| Stock Option Tax Benefits [Member]                                                                        |                                                                                                                          |                                                                                                         |   |   |   |
| **Operating Loss Carryforwards [Line Items]**                                                             |                                                                                                                          |                                                                                                         |   |   |   |
| Deferred Tax Assets, Operating Loss Carryforwards                                                         | $ 62us-gaap_DeferredTaxAssetsOperatingLossCarryforwards/ nav_OperatingLossCarryforwardsAxis= nav_StockOptionTaxBenefitsMember |                                                                                                         | $ 62us-gaap_DeferredTaxAssetsOperatingLossCarryforwards/ nav_OperatingLossCarryforwardsAxis= nav_StockOptionTaxBenefitsMember |   |   |
| Minimum [Member]                                                                                          |                                                                                                                          |                                                                                                         |   |   |   |
| **Operating Loss Carryforwards [Line Items]**                                                             |                                                                                                                          |                                                                                                         |   |   |   |
| Operating Loss Carryforwards, Duration of Carryforward                                                    |                                                                                                                          |                                                                                                         | 5 years |   |   |
| Maximum [Member]                                                                                          |                                                                                                                          |                                                                                                         |   |   |   |
| **Operating Loss Carryforwards [Line Items]**                                                             |                                                                                                                          |                                                                                                         |   |   |   |
| Operating Loss Carryforwards, Duration of Carryforward                                                    |                                                                                                                          |                                                                                                         | 20 years |   |   |

| X                                                                                                                                                                                                                                                                                                        |
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Income Taxes Percent Likelihood Of Being Realized Upon Settlement
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offsetting tax benefits associated with the correlative effects of potential transfer pricing adjustments
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Unrecognized Tax Benefits that Would Not Impact Effective Tax Rate
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| - Definition
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.
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| - Definition
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards. Excludes state and local operating loss carryforwards.
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| - Definition
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible foreign operating loss carryforwards.
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| - Definition
Amount before allocation of valuation allowances of deferred tax asset attributable to deductible state and local operating loss carryforwards.
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| - Definition
Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.
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| - Definition
Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of undistributed earnings of foreign subsidiaries intended to be permanently reinvested outside the country of domicile.
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| - Definition
Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.
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| - Definition
Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.
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| - Definition
Amount of expense for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.
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Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.
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