| **Condensed Consolidating Guarantor and Non-Guarantor Financial Information - Statement of Cash Flows (Details) - USD ($) $ in Millions** | 6 Months Ended |
|-------------------------------------------------------------------------------------------------------------------------------------------|----------------|
||
| Net cash provided by (used in) operations                                                                                                 | $ (104)        | $ (237) |
| Net change in restricted cash and cash equivalents                                                                                        | (19)           | 53 |
| Net sales (purchases) of marketable securities                                                                                            | (69)           | 332 |
| Capital expenditures and purchase of equipment leased to others                                                                           | (131)          | (65) |
| Other investing activities                                                                                                                | 53             | 12 |
| Net cash provided by (used in) investing activities                                                                                       | (166)          | 332 |
| Net borrowings (repayments) of debt                                                                                                       | (65)           | 16 |
| Other financing activities                                                                                                                | (6)            | 1 |
| Net cash provided by (used in) financing activities                                                                                       | (71)           | 17 |
| Effect of exchange rate changes on cash and cash equivalents                                                                              | 18             | (26) |
| Increase (decrease) in cash and cash equivalents                                                                                          | (323)          | 86 |
| Cash and cash equivalents at beginning of the period                                                                                      | 912            | 497 |
| Cash and cash equivalents at end of the period                                                                                            | 589            | 583 |
| Parent Company [Member]                                                                                                                   |           |   |
| Net cash provided by (used in) operations                                                                                                 | (293)          | (168) |
| Net change in restricted cash and cash equivalents                                                                                        | 0              | 1 |
| Net sales (purchases) of marketable securities                                                                                            | 65             | 229 |
| Capital expenditures and purchase of equipment leased to others                                                                           | 0              | 0 |
| Other investing activities                                                                                                                | 0              | 0 |
| Net cash provided by (used in) investing activities                                                                                       | 65             | 230 |
| Net borrowings (repayments) of debt                                                                                                       | 0              | 0 |
| Other financing activities                                                                                                                | 0              | 0 |
| Net cash provided by (used in) financing activities                                                                                       | 0              | 0 |
| Effect of exchange rate changes on cash and cash equivalents                                                                              | 0              | 0 |
| Increase (decrease) in cash and cash equivalents                                                                                          | (228)          | 62 |
| Cash and cash equivalents at beginning of the period                                                                                      | 456            | 101 |
| Cash and cash equivalents at end of the period                                                                                            | 228            | 163 |
| Guarantor Subsidiaries [Member]                                                                                                           |           |   |
| Net cash provided by (used in) operations                                                                                                 | (297)          | 41 |
| Net change in restricted cash and cash equivalents                                                                                        | 2              | (2) |
| Net sales (purchases) of marketable securities                                                                                            | 0              | 0 |
| Capital expenditures and purchase of equipment leased to others                                                                           | (34)           | (30) |
| Other investing activities                                                                                                                | 0              | 7 |
| Net cash provided by (used in) investing activities                                                                                       | (32)           | (25) |
| Net borrowings (repayments) of debt                                                                                                       | 259            | (52) |
| Other financing activities                                                                                                                | 13             | 20 |
| Net cash provided by (used in) financing activities                                                                                       | 272            | (32) |
| Effect of exchange rate changes on cash and cash equivalents                                                                              | 0              | 0 |
| Increase (decrease) in cash and cash equivalents                                                                                          | (57)           | (16) |
| Cash and cash equivalents at beginning of the period                                                                                      | 81             | 53 |
| Cash and cash equivalents at end of the period                                                                                            | 24             | 37 |
| Non-Guarantor Subsidiaries [Member]                                                                                                       |           |   |
| Net cash provided by (used in) operations                                                                                                 | 218            | (188) |
| Net change in restricted cash and cash equivalents                                                                                        | (21)           | 54 |
| Net sales (purchases) of marketable securities                                                                                            | (134)          | 103 |
| Capital expenditures and purchase of equipment leased to others                                                                           | (97)           | (35) |
| Other investing activities                                                                                                                | 53             | 5 |
| Net cash provided by (used in) investing activities                                                                                       | (199)          | 127 |
| Net borrowings (repayments) of debt                                                                                                       | (26)           | 66 |
| Other financing activities                                                                                                                | (49)           | 61 |
| Net cash provided by (used in) financing activities                                                                                       | (75)           | 127 |
| Effect of exchange rate changes on cash and cash equivalents                                                                              | 18             | (26) |
| Increase (decrease) in cash and cash equivalents                                                                                          | (38)           | 40 |
| Cash and cash equivalents at beginning of the period                                                                                      | 375            | 343 |
| Cash and cash equivalents at end of the period                                                                                            | 337            | 383 |
| Consolidation, Eliminations [Member]                                                                                                      |           |   |
| Net cash provided by (used in) operations                                                                                                 | 268            | 78 |
| Net change in restricted cash and cash equivalents                                                                                        | 0              | 0 |
| Net sales (purchases) of marketable securities                                                                                            | 0              | 0 |
| Capital expenditures and purchase of equipment leased to others                                                                           | 0              | 0 |
| Other investing activities                                                                                                                | 0              | 0 |
| Net cash provided by (used in) investing activities                                                                                       | 0              | 0 |
| Net borrowings (repayments) of debt                                                                                                       | (298)          | 2 |
| Other financing activities                                                                                                                | 30             | (80) |
| Net cash provided by (used in) financing activities                                                                                       | (268)          | (78) |
| Effect of exchange rate changes on cash and cash equivalents                                                                              | 0              | 0 |
| Increase (decrease) in cash and cash equivalents                                                                                          | 0              | 0 |
| Cash and cash equivalents at beginning of the period                                                                                      | 0              | 0 |
| Cash and cash equivalents at end of the period                                                                                            | $ 0            | $ 0 |

| X                                                                                                                                                                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Cash and cash equivalents at beginning of the period
+ References
No definition available.
+ Details**Name:**nav_CashAndCashEquivalentsAtBeginningOfPeriod**Namespace Prefix:**nav_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Cash and cash equivalents at end of the period
+ References
No definition available.
+ Details**Name:**nav_CashAndCashEquivalentsAtEndOfPeriod**Namespace Prefix:**nav_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Net Cash Provided by (Used in) Financing Activities, Excluding Net Borrowings (Repayments) of Debt
+ References
No definition available.
+ Details**Name:**nav_NetCashProvidedbyUsedinFinancingActivitiesExcludingNetBorrowingsRepaymentsofDebt**Namespace Prefix:**nav_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3521-108585Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49171198&loc=d3e33268-110906
+ Details**Name:**us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of increase (decrease) from the effect of exchange rate changes on cash and cash equivalent balances held in foreign currencies.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49171198&loc=d3e33268-110906
+ Details**Name:**us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The net cash inflow or outflow for the increase (decrease) associated with funds that are not available for withdrawal or use (such as funds held in escrow) and are associated with underlying transactions that are classified as investing activities.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3179-108585Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133
+ Details**Name:**us-gaap_IncreaseDecreaseInRestrictedCash**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3521-108585Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3574-108585
+ Details**Name:**us-gaap_NetCashProvidedByUsedInFinancingActivities**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3521-108585Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3574-108585
+ Details**Name:**us-gaap_NetCashProvidedByUsedInInvestingActivities**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3521-108585Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3536-108585
+ Details**Name:**us-gaap_NetCashProvidedByUsedInOperatingActivities**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The net cash paid (received) associated with the acquisition or disposal of all investments, including securities and other assets.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3098-108585Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3095-108585
+ Details**Name:**us-gaap_PaymentsForProceedsFromInvestments**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of cash (inflow) outflow from investing activities classified as other.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3098-108585Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3095-108585
+ Details**Name:**us-gaap_PaymentsForProceedsFromOtherInvestingActivities**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585
+ Details**Name:**us-gaap_PaymentsToAcquireProductiveAssets**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The net cash inflow or outflow in aggregate debt due to repayments and proceeds from additional borrowings.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228
+ Details**Name:**us-gaap_ProceedsFromRepaymentsOfDebt**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                       |
|-----------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**dei_LegalEntityAxis=us-gaap_ParentCompanyMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**dei_LegalEntityAxis=us-gaap_GuarantorSubsidiariesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**dei_LegalEntityAxis=us-gaap_NonGuarantorSubsidiariesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_ConsolidationItemsAxis=us-gaap_ConsolidationEliminationsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |