| **Stockholders' Deficit - Narrative (Details) (USD $)In Millions, except Share data, unless otherwise specified**                       | 3 Months Ended                                                                                                      | 12 Months Ended                                                                                                                                         | 1 Months Ended                                                                                                                       | 3 Months Ended                                                                                                                                                                                                                            |                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                          |
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| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Stock Repurchase Program, Authorized Amount                                                                                             |                                                                                                                | $ 75us-gaap_StockRepurchaseProgramAuthorizedAmount1                                                                                                     |                                                                                                                                 |                                                                                                                                                                                                                                      | $ 75us-gaap_StockRepurchaseProgramAuthorizedAmount1                                                                                                     |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Common stock, shares issued                                                                                                             |                                                                                                                |                                                                                                                                                    | 81,400,000us-gaap_CommonStockSharesIssued                                                                                            | 80,500,000us-gaap_CommonStockSharesIssued                                                                                                                                                                                                 |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock, Shares Authorized                                                                                                      |                                                                                                                |                                                                                                                                                    | 30,000,000us-gaap_PreferredStockSharesAuthorized                                                                                     |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Proceeds from Issuance of Common Stock                                                                                                  | 14us-gaap_ProceedsFromIssuanceOfCommonStock                                                                         | 192us-gaap_ProceedsFromIssuanceOfCommonStock                                                                                                            | 0us-gaap_ProceedsFromIssuanceOfCommonStock                                                                                           | 14us-gaap_ProceedsFromIssuanceOfCommonStock                                                                                                                                                                                               | 192us-gaap_ProceedsFromIssuanceOfCommonStock                                                                                                            |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock, Shares Issued                                                                                                          |                                                                                                                |                                                                                                                                                    | 0us-gaap_PreferredStockSharesIssued                                                                                                  |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock, Par or Stated Value Per Share                                                                                          |                                                                                                                |                                                                                                                                                    | $ 1us-gaap_PreferredStockParOrStatedValuePerShare                                                                                    |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Debt Instrument, Unamortized Discount                                                                                                   |                                                                                                                |                                                                                                                                                    | 82us-gaap_DebtInstrumentUnamortizedDiscount                                                                                          |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Payments for Repurchase of Common Stock                                                                                                 |                                                                                                                |                                                                                                                                                    | 0us-gaap_PaymentsForRepurchaseOfCommonStock                                                                                          | 0us-gaap_PaymentsForRepurchaseOfCommonStock                                                                                                                                                                                               | 75us-gaap_PaymentsForRepurchaseOfCommonStock                                                                                                            |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Common stock, shares authorized                                                                                                         |                                                                                                                |                                                                                                                                                    | 220,000,000us-gaap_CommonStockSharesAuthorized                                                                                       | 220,000,000us-gaap_CommonStockSharesAuthorized                                                                                                                                                                                            |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Common stock, par value                                                                                                                 |                                                                                                                |                                                                                                                                                    | $ 0.10us-gaap_CommonStockParOrStatedValuePerShare                                                                                    | $ 0.10us-gaap_CommonStockParOrStatedValuePerShare                                                                                                                                                                                         |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock [Member]                                                                                                                |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Class of Warrant or Right, Number of Securities Called by Each Warrant or Right                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   | 0.001us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight/ us-gaap_StatementClassOfStockAxis= us-gaap_PreferredStockMember |   |   |
| Series A Preferred Stock [Member]                                                                                                       |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock, Shares Authorized                                                                                                      |                                                                                                                | 220,000us-gaap_PreferredStockSharesAuthorized/ us-gaap_StatementClassOfStockAxis= us-gaap_SeriesAPreferredStockMember                                   |                                                                                                                                 |                                                                                                                                                                                                                                      | 220,000us-gaap_PreferredStockSharesAuthorized/ us-gaap_StatementClassOfStockAxis= us-gaap_SeriesAPreferredStockMember                                   |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   | 110,000us-gaap_PreferredStockSharesAuthorized/ us-gaap_StatementClassOfStockAxis= us-gaap_SeriesAPreferredStockMember |   |
| Preferred Stock, Par or Stated Value Per Share                                                                                          |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   | $ 1us-gaap_PreferredStockParOrStatedValuePerShare/ us-gaap_StatementClassOfStockAxis= us-gaap_SeriesAPreferredStockMember |   |
| Common Stock [Member]                                                                                                                   |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Stock Issued During Period, Shares, New Issues                                                                                          | 763,534us-gaap_StockIssuedDuringPeriodSharesNewIssues/ us-gaap_StatementClassOfStockAxis= us-gaap_CommonStockMember | 10,666,666us-gaap_StockIssuedDuringPeriodSharesNewIssues/ us-gaap_StatementClassOfStockAxis= us-gaap_CommonStockMember                                  |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Share Price                                                                                                                             | $ 18.75us-gaap_SharePrice/ us-gaap_StatementClassOfStockAxis= us-gaap_CommonStockMember                             | $ 18.75us-gaap_SharePrice/ us-gaap_StatementClassOfStockAxis= us-gaap_CommonStockMember                                                                 |                                                                                                                                 |                                                                                                                                                                                                                                      | $ 18.75us-gaap_SharePrice/ us-gaap_StatementClassOfStockAxis= us-gaap_CommonStockMember                                                                 |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preference Stock [Member]                                                                                                               |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock, Shares Authorized                                                                                                      |                                                                                                                | 10,000,000us-gaap_PreferredStockSharesAuthorized/ us-gaap_StatementClassOfStockAxis= nav_PreferenceStockMember                                          |                                                                                                                                 |                                                                                                                                                                                                                                      | 10,000,000us-gaap_PreferredStockSharesAuthorized/ us-gaap_StatementClassOfStockAxis= nav_PreferenceStockMember                                          |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock, Par or Stated Value Per Share                                                                                          |                                                                                                                | $ 1.00us-gaap_PreferredStockParOrStatedValuePerShare/ us-gaap_StatementClassOfStockAxis= nav_PreferenceStockMember                                      |                                                                                                                                 |                                                                                                                                                                                                                                      | $ 1.00us-gaap_PreferredStockParOrStatedValuePerShare/ us-gaap_StatementClassOfStockAxis= nav_PreferenceStockMember                                      |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Convertible Junior Preference Stock Series D [Member]                                                                                   |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock, Par or Stated Value Per Share                                                                                          |                                                                                                                | $ 1.00us-gaap_PreferredStockParOrStatedValuePerShare/ us-gaap_StatementClassOfStockAxis= nav_ConvertibleJuniorPreferenceStockSeriesDMember              |                                                                                                                                 |                                                                                                                                                                                                                                      | $ 1.00us-gaap_PreferredStockParOrStatedValuePerShare/ us-gaap_StatementClassOfStockAxis= nav_ConvertibleJuniorPreferenceStockSeriesDMember              |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock, Shares Outstanding                                                                                                     |                                                                                                                |                                                                                                                                                    | 100,702us-gaap_PreferredStockSharesOutstanding/ us-gaap_StatementClassOfStockAxis= nav_ConvertibleJuniorPreferenceStockSeriesDMember | 120,096us-gaap_PreferredStockSharesOutstanding/ us-gaap_StatementClassOfStockAxis= nav_ConvertibleJuniorPreferenceStockSeriesDMember                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock, Liquidation Preference Per Share                                                                                       |                                                                                                                | $ 25us-gaap_PreferredStockLiquidationPreference/ us-gaap_StatementClassOfStockAxis= nav_ConvertibleJuniorPreferenceStockSeriesDMember                   |                                                                                                                                 |                                                                                                                                                                                                                                      | $ 25us-gaap_PreferredStockLiquidationPreference/ us-gaap_StatementClassOfStockAxis= nav_ConvertibleJuniorPreferenceStockSeriesDMember                   |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Convertible Preferred Stock, Shares Issued upon Conversion                                                                              |                                                                                                                | 0.3125us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion/ us-gaap_StatementClassOfStockAxis= nav_ConvertibleJuniorPreferenceStockSeriesDMember |                                                                                                                                 |                                                                                                                                                                                                                                      | 0.3125us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion/ us-gaap_StatementClassOfStockAxis= nav_ConvertibleJuniorPreferenceStockSeriesDMember |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Preferred Stock, Dividend Rate, Percentage                                                                                              |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      | 120.00%us-gaap_PreferredStockDividendRatePercentage/ us-gaap_StatementClassOfStockAxis= nav_ConvertibleJuniorPreferenceStockSeriesDMember               |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Three Point Zero Percent Senior Subordinated Convertible Notes [Member]                                                                 |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Proceeds from Issuance of Warrants                                                                                                      |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      | 87us-gaap_ProceedsFromIssuanceOfWarrants/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember                 |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Three Point Zero Percent Senior Subordinated Convertible Notes [Member] | Call Option [Member] | Convertible Subordinated Debt [Member] |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Payments for Derivative Instrument, Investing Activities                                                                                |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    | 125us-gaap_PaymentsForDerivativeInstrumentInvestingActivities/ us-gaap_DebtInstrumentAxis= nav_ThreePointZeroPercentSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember/ us-gaap_OptionIndexedToIssuersEquityEquityAxis= us-gaap_CallOptionMember |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Four Point Five Zero Senior Subordinated Convertible Notes [Member] | Convertible Subordinated Debt [Member]                            |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Long-term Debt, Fair Value                                                                                                              |                                                                                                                |                                                                                                                                                    |                                                                                                                                 | 177us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Debt Instrument, Convertible, Carrying Amount of Equity Component                                                                       |                                                                                                                |                                                                                                                                                    |                                                                                                                                 | 22us-gaap_DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Debt Instrument, Unamortized Discount                                                                                                   |                                                                                                                |                                                                                                                                                    |                                                                                                                                 | 1us-gaap_DebtInstrumentUnamortizedDiscount/ us-gaap_DebtInstrumentAxis= nav_FourPointFiveZeroSeniorSubordinatedConvertibleNotesMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember                            |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Four Point Seven Five Senior Subordinated Convertible Notes [Member] [Member] | Convertible Subordinated Debt [Member]                  |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Long-term Debt, Fair Value                                                                                                              |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   | 367us-gaap_LongTermDebtFairValue/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember |
| Debt Instrument, Convertible, Carrying Amount of Equity Component                                                                       |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   | 44us-gaap_DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember |
| Debt Instrument, Unamortized Discount                                                                                                   |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   | 1us-gaap_DebtInstrumentUnamortizedDiscount/ us-gaap_DebtInstrumentAxis= nav_FourPointSevenFiveSeniorSubordinatedConvertibleNotesMemberMember/ us-gaap_LongtermDebtTypeAxis= us-gaap_ConvertibleSubordinatedDebtMember |
| Maximum [Member]                                                                                                                        |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Stock Repurchase Program, Authorized Amount                                                                                             |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     | 175us-gaap_StockRepurchaseProgramAuthorizedAmount1/ us-gaap_RangeAxis= us-gaap_MaximumMember |   |   |   |   |   |   |
| Accelerated Share Repurchases Program [Member]                                                                                          |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Stock Repurchase Program, Authorized Amount                                                                                             |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     | 100us-gaap_StockRepurchaseProgramAuthorizedAmount1/ nav_AcceleratedShareRepurchasesAxis= nav_AcceleratedShareRepurchasesProgramMember |   |   |   |   |   |   |
| Treasury Stock, Shares, Acquired                                                                                                        |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            | 2,542,609us-gaap_TreasuryStockSharesAcquired/ nav_AcceleratedShareRepurchasesAxis= nav_AcceleratedShareRepurchasesProgramMember                                                                          |   |   |   |   |   |   |   |
| Stock Repurchase Program, Remaining Authorized Repurchase Amount                                                                        |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     | 20us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1/ nav_AcceleratedShareRepurchasesAxis= nav_AcceleratedShareRepurchasesProgramMember |   |   |   |   |   |   |
| October 2011 [Member]                                                                                                                   |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Accelerated Share Repurchases, Settlement (Payment) or Receipt                                                                          |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   | 80us-gaap_AcceleratedShareRepurchasesSettlementPaymentOrReceipt/ us-gaap_AcceleratedShareRepurchasesDateAxis= nav_October2011Member |   | 80us-gaap_AcceleratedShareRepurchasesSettlementPaymentOrReceipt/ us-gaap_AcceleratedShareRepurchasesDateAxis= nav_October2011Member |   |   |   |
| Accelerated Share Repurchases, Initial Price Paid Per Share                                                                             |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     | $ 33.60us-gaap_AcceleratedShareRepurchasesInitialPricePaidPerShare/ us-gaap_AcceleratedShareRepurchasesDateAxis= nav_October2011Member |   |   |   |   |   |   |
| October 2011 [Member] | Accelerated Share Repurchases Program [Member]                                                                  |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Treasury Stock, Shares, Acquired                                                                                                        |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     | 2,380,952us-gaap_TreasuryStockSharesAcquired/ nav_AcceleratedShareRepurchasesAxis= nav_AcceleratedShareRepurchasesProgramMember/ us-gaap_AcceleratedShareRepurchasesDateAxis= nav_October2011Member |   |   |   |   |   |   |
| November 2011 [Member]                                                                                                                  |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Accelerated Share Repurchases, Settlement (Payment) or Receipt                                                                          |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   | 20us-gaap_AcceleratedShareRepurchasesSettlementPaymentOrReceipt/ us-gaap_AcceleratedShareRepurchasesDateAxis= nav_November2011Member |   | 20us-gaap_AcceleratedShareRepurchasesSettlementPaymentOrReceipt/ us-gaap_AcceleratedShareRepurchasesDateAxis= nav_November2011Member |   |   |   |
| November 2011 [Member] | Accelerated Share Repurchases Program [Member]                                                                 |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Treasury Stock, Additional Shares Acquired                                                                                              |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            | 161,657nav_TreasuryStockAdditionalSharesAcquired/ nav_AcceleratedShareRepurchasesAxis= nav_AcceleratedShareRepurchasesProgramMember/ us-gaap_AcceleratedShareRepurchasesDateAxis= nav_November2011Member |   |   |   |   |   |   |   |
| Open Market Share Repurchase Program [Member]                                                                                           |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| **Class of Stock [Line Items]**                                                                                                         |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   |   |   |   |   |   |
| Stock Repurchase Program, Authorized Amount                                                                                             |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     | 75us-gaap_StockRepurchaseProgramAuthorizedAmount1/ nav_OpenMarketShareRepurchaseAxis= nav_OpenMarketShareRepurchaseProgramMember |   |   |   |   |   |   |
| Treasury Stock, Shares, Acquired                                                                                                        |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   | 1,905,600us-gaap_TreasuryStockSharesAcquired/ nav_OpenMarketShareRepurchaseAxis= nav_OpenMarketShareRepurchaseProgramMember |   |   |   |   |   |
| Payments for Repurchase of Common Stock                                                                                                 |                                                                                                                |                                                                                                                                                    |                                                                                                                                 |                                                                                                                                                                                                                                      |                                                                                                                                                    |                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                     |   |   | $ 5us-gaap_PaymentsForRepurchaseOfCommonStock/ nav_OpenMarketShareRepurchaseAxis= nav_OpenMarketShareRepurchaseProgramMember | $ 70us-gaap_PaymentsForRepurchaseOfCommonStock/ nav_OpenMarketShareRepurchaseAxis= nav_OpenMarketShareRepurchaseProgramMember |   |   |   |

| X                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Treasury Stock, Additional Shares Acquired
+ References
No definition available.
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| - Definition
The price paid per share to immediately purchase the targeted number of shares on the date of executing the accelerated share repurchase agreement.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of cash receipt from (payment to) bank; or stock received from (issuance to) bank in the settlement of the accelerated share repurchase agreement.
+ References
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of securities into which each warrant or right may be converted. For example, but not limited to, each warrant may be converted into two shares.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Face amount or stated value per share of common stock.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The maximum number of common shares permitted to be issued by an entity's charter and bylaws.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.
+ References
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of shares issued for each share of convertible preferred stock that is converted.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash outflow for derivative instruments during the period, which are classified as investing activities, excluding those designated as hedging instruments.
+ References
No definition available.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash outflow to reacquire common stock during the period.
+ References
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| X                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The percentage rate used to calculate dividend payments on preferred stock.
+ References
No definition available.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share.
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash inflow from the additional capital contribution to the entity.
+ References
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash inflow from issuance of rights to purchase common shares at predetermined price (usually issued together with corporate debt).
+ References
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| X                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Price of a single share of a number of saleable stocks of a company.
+ References
No definition available.
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|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of new stock issued during the period.
+ References
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| X                                                                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of stock repurchase plan authorized.
+ References
No definition available.
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| - Definition
Amount remaining of a stock repurchase plan authorized.
+ References
No definition available.
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Number of shares that have been repurchased during the period and are being held in treasury.
+ References
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