| **Allowance for Doubtful Accounts - Schedule of Allowance for Retail, Wholesale, Trade & Other (Details) - USD ($) $ in Millions** | 3 Months Ended | 9 Months Ended |
|----------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Allowance for Doubtful Accounts Receivable [Roll Forward]**                                                                          |           |           |   |   |
| Allowance for doubtful accounts at beginning of period                                                                                 | $ 51           | $ 58           | $ 48 | $ 65 |
| Provision for doubtful accounts, net of recoveries                                                                                     | 1              | 2              | 8 | 7 |
| Charge-off of accounts                                                                                                                 | (4)            | (1)            | (9) | (5) |
| Allowance for doubtful accounts at end of period                                                                                       | 48             | 54             | 48 | 54 |
| Financing Receivable, Allowance for Credit Losses, Other                                                                               | 0              | (5)            | 1 | (13) |
| Retail Portfolio [Member]                                                                                                              |           |           |   |   |
| **Allowance for Doubtful Accounts Receivable [Roll Forward]**                                                                          |           |           |   |   |
| Allowance for doubtful accounts at beginning of period                                                                                 | 21             | 25             | 22 | 24 |
| Provision for doubtful accounts, net of recoveries                                                                                     | 2              | 2              | 5 | 7 |
| Charge-off of accounts                                                                                                                 | (3)            | 0              | (7) | (1) |
| Allowance for doubtful accounts at end of period                                                                                       | 18             | 25             | 18 | 25 |
| Financing Receivable, Allowance for Credit Losses, Other                                                                               | (2)            | (2)            | 2 | (5) |
| Impaired Financing Receivable, Average Recorded Investment                                                                             |           |           | 18 | 21 |
| Wholesale Portfolio [Member]                                                                                                           |           |           |   |   |
| **Allowance for Doubtful Accounts Receivable [Roll Forward]**                                                                          |           |           |   |   |
| Allowance for doubtful accounts at beginning of period                                                                                 | 4              | 3              | 4 | 3 |
| Provision for doubtful accounts, net of recoveries                                                                                     | (1)            | 0              | (1) | 0 |
| Charge-off of accounts                                                                                                                 | 0              | 0              | 0 | 0 |
| Allowance for doubtful accounts at end of period                                                                                       | 3              | 3              | 3 | 3 |
| Financing Receivable, Allowance for Credit Losses, Other                                                                               | 0              | 0              | 0 | 0 |
| Trade and Other Receivables [Member]                                                                                                   |           |           |   |   |
| **Allowance for Doubtful Accounts Receivable [Roll Forward]**                                                                          |           |           |   |   |
| Allowance for doubtful accounts at beginning of period                                                                                 | 26             | 30             | 22 | 38 |
| Provision for doubtful accounts, net of recoveries                                                                                     | 0              | 0              | 4 | 0 |
| Charge-off of accounts                                                                                                                 | (1)            | (1)            | (2) | (4) |
| Allowance for doubtful accounts at end of period                                                                                       | 27             | 26             | 27 | 26 |
| Financing Receivable, Allowance for Credit Losses, Other                                                                               | $ 2            | $ (3)          | $ 3 | $ (8) |

| X                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing Receivable, Allowance for Credit Losses, Other
+ References
No definition available.
+ Details**Name:**nav_FinancingReceivableAllowanceforCreditLossesOther**Namespace Prefix:**nav_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.
+ References
No definition available.
+ Details**Name:**us-gaap_AllowanceForDoubtfulAccountsReceivableRollforward**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
A valuation allowance for financing receivables that are expected to be uncollectible.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524
+ Details**Name:**us-gaap_FinancingReceivableAllowanceForCreditLosses**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of direct write-downs of financing receivables charged against the allowance.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524
+ Details**Name:**us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5212-111524Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5258-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.11) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585
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| X                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                          |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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