| **Summary of Significant Accounting Policies - Product Warranty Liability (Details) (USD $)In Millions, except Per Share data, unless otherwise specified** | 6 Months Ended                                                                                                             | 3 Months Ended                                                                                                             |                                                                                                                            |                                                                                                                                                                                                             |
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| **Product Liability Contingency [Line Items]**                                                                                                              |                                                                                                                       |                                                                                                                       |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| Product Warranty Accrual                                                                                                                                    | $ 1,059us-gaap_ProductWarrantyAccrual                                                                                      | $ 1,323us-gaap_ProductWarrantyAccrual                                                                                      | $ 1,059us-gaap_ProductWarrantyAccrual                                                                                      | $ 1,323us-gaap_ProductWarrantyAccrual                                                                                                                                                                       |   |   | $ 1,197us-gaap_ProductWarrantyAccrual | $ 1,349us-gaap_ProductWarrantyAccrual |
| Product Warranty Accrual, Warranties Issued                                                                                                                 | 116us-gaap_ProductWarrantyAccrualWarrantiesIssued                                                                          | 153us-gaap_ProductWarrantyAccrualWarrantiesIssued                                                                          |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| Product Warranty Accrual, Currency Translation, Increase (Decrease)                                                                                         | (5)us-gaap_ProductWarrantyAccrualCurrencyTranslationIncreaseDecrease                                                       | (1)us-gaap_ProductWarrantyAccrualCurrencyTranslationIncreaseDecrease                                                       |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| **Accrued Product Warranty And Deferred Warranty Revenue, Standard And Extended Warranty Programs, Roll Forward:**                                          |                                                                                                                       |                                                                                                                       |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| Adjustments to pre-existing warranties(A)(B)                                                                                                                | (39)us-gaap_ProductWarrantyAccrualPreexistingIncreaseDecrease                                                              | 94us-gaap_ProductWarrantyAccrualPreexistingIncreaseDecrease                                                                |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| **Extended Warranty Program:**                                                                                                                              |                                                                                                                       |                                                                                                                       |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| Product Warranty Accrual, Payments                                                                                                                          | (210)us-gaap_ProductWarrantyAccrualPayments                                                                                | (272)us-gaap_ProductWarrantyAccrualPayments                                                                                |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| Product Warranty Accrual, Current                                                                                                                           | 496us-gaap_ProductWarrantyAccrualClassifiedCurrent                                                                         | 626us-gaap_ProductWarrantyAccrualClassifiedCurrent                                                                         | 496us-gaap_ProductWarrantyAccrualClassifiedCurrent                                                                         | 626us-gaap_ProductWarrantyAccrualClassifiedCurrent                                                                                                                                                          |   |   |   |   |
| Product Warranty Accrual, Noncurrent                                                                                                                        | 563us-gaap_ProductWarrantyAccrualNoncurrent                                                                                | 697us-gaap_ProductWarrantyAccrualNoncurrent                                                                                | 563us-gaap_ProductWarrantyAccrualNoncurrent                                                                                | 697us-gaap_ProductWarrantyAccrualNoncurrent                                                                                                                                                                 |   |   |   |   |
| Extended Warranty Programs [Member]                                                                                                                         |                                                                                                                       |                                                                                                                       |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| **Extended Warranty Program:**                                                                                                                              |                                                                                                                       |                                                                                                                       |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| Deferred Revenue, Revenue Recognized                                                                                                                        | 75us-gaap_DeferredRevenueRevenueRecognized/ us-gaap_DeferredRevenueArrangementTypeAxis= nav_ExtendedWarrantyProgramsMember | 60us-gaap_DeferredRevenueRevenueRecognized/ us-gaap_DeferredRevenueArrangementTypeAxis= nav_ExtendedWarrantyProgramsMember | 38us-gaap_DeferredRevenueRevenueRecognized/ us-gaap_DeferredRevenueArrangementTypeAxis= nav_ExtendedWarrantyProgramsMember | 33us-gaap_DeferredRevenueRevenueRecognized/ us-gaap_DeferredRevenueArrangementTypeAxis= nav_ExtendedWarrantyProgramsMember                                                                                  |   |   |   |   |
| Deferred Revenue                                                                                                                                            | 425us-gaap_DeferredRevenue/ us-gaap_DeferredRevenueArrangementTypeAxis= nav_ExtendedWarrantyProgramsMember                 |                                                                                                                       | 425us-gaap_DeferredRevenue/ us-gaap_DeferredRevenueArrangementTypeAxis= nav_ExtendedWarrantyProgramsMember                 |                                                                                                                                                                                                        |   |   | 437us-gaap_DeferredRevenue/ us-gaap_DeferredRevenueArrangementTypeAxis= nav_ExtendedWarrantyProgramsMember |   |
| Product Warranty Accrual [Member]                                                                                                                           |                                                                                                                       |                                                                                                                       |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| **Accrued Product Warranty And Deferred Warranty Revenue, Standard And Extended Warranty Programs, Roll Forward:**                                          |                                                                                                                       |                                                                                                                       |                                                                                                                       |                                                                                                                                                                                                        |   |   |   |   |
| Adjustments to pre-existing warranties(A)(B)                                                                                                                |                                                                                                                       |                                                                                                                       |                                                                                                                       | $ 42us-gaap_ProductWarrantyAccrualPreexistingIncreaseDecrease/ us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis= nav_ProductWarrantyAccrualMember               | $ (57)us-gaap_ProductWarrantyAccrualPreexistingIncreaseDecrease/ us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis= nav_ProductWarrantyAccrualMember | $ 52us-gaap_ProductWarrantyAccrualPreexistingIncreaseDecrease/ us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis= nav_ProductWarrantyAccrualMember |   |   |
| Product Warranty Accrual, Preexisting Increase Decrease Per Share, Net of Tax                                                                               |                                                                                                                       |                                                                                                                       |                                                                                                                       | $ 0.52nav_ProductWarrantyAccrualPreexistingIncreaseDecreasePerShareNetOfTax/ us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis= nav_ProductWarrantyAccrualMember | $ (0.70)nav_ProductWarrantyAccrualPreexistingIncreaseDecreasePerShareNetOfTax/ us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis= nav_ProductWarrantyAccrualMember | $ 0.64nav_ProductWarrantyAccrualPreexistingIncreaseDecreasePerShareNetOfTax/ us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis= nav_ProductWarrantyAccrualMember |   |   |

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| - Definition
Product Warranty Accrual, Preexisting Increase Decrease Per Share, Net of Tax
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| - Definition
Amount of deferred revenue as of balance sheet date. Deferred revenue represents collections of cash or other assets related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.
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| - Definition
Amount of previously reported deferred or unearned revenue that was recognized as revenue during the period. Deferred revenue is a liability related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.
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| - Definition
Carrying value as of the balance sheet date of obligations incurred through that date and payable for estimated claims under standard and extended warranty protection rights granted to customers.
+ References
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| - Definition
Carrying value as of the balance sheet date of obligations incurred through that date and payable for estimated claims under standard and extended warranty protection rights granted to customers. For classified balance sheets, represents the current portion of the liabilities (due within one year or within the normal operating cycle if longer).
+ References
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| - Definition
Total Increase or Decrease in the standard and extended product warranty liability due to currency translation.
+ References
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| - Definition
Carrying value as of the balance sheet date of obligations incurred through that date and due after one year (or beyond the operating cycle if longer) for estimated claims under standard and extended warranty protection rights granted to customers.
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| - Definition
Represents the aggregate decrease in the liability related to payments to satisfy claims for standard and extended product warranties.
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| - Definition
Represents the aggregate Increase or Decrease in the liability during the reporting period for accruals related to preexisting standard and extended product warranties (including adjustments for changes in estimates).
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| - Definition
Represents the aggregate increase in the liability for accruals related to standard and extended product warranties issued during the reporting period.
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