| **Allowance for Doubtful Accounts Aging Analysis (Details) (USD $)In Millions** | Jul. 31, 2011 |
|---------------------------------------------------------------------------------|---------------|
| **Financing Receivable, Recorded Investment, Past Due [Line Items]**            | Â             |
| Current                                                                         | $ 2,733       |
| 30-90 days past due                                                             | 86            |
| Over 90 days past due                                                           | 15            |
| Total finance receivables                                                       | 2,834         |
| Retail Portfolio [Member]                                                       | Â             |
| **Financing Receivable, Recorded Investment, Past Due [Line Items]**            | Â             |
| Current                                                                         | 1,521         |
| 30-90 days past due                                                             | 83            |
| Over 90 days past due                                                           | 14            |
| Total finance receivables                                                       | 1,618         |
| Wholesale Portfolio [Member]                                                    | Â             |
| **Financing Receivable, Recorded Investment, Past Due [Line Items]**            | Â             |
| Current                                                                         | 1,212         |
| 30-90 days past due                                                             | 3             |
| Over 90 days past due                                                           | 1             |
| Total finance receivables                                                       | $ 1,216       |

| X                                                                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Reflects gross amount of all categories of loans and leases held in portfolio due from customers, clients, lessees, borrowers, or others.
+ Details**Name:**nav_FinanceReceivablesGross**Namespace Prefix:**nav**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                    |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing Receivables Recorded Investment 30 To 90 Days Past Due
+ Details**Name:**nav_FinancingReceivablesRecordedInvestment30To90DaysPastDue**Namespace Prefix:**nav**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing receivables that are current.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=6965416&loc=SL6953401-111524
+ Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentCurrent**Namespace Prefix:**us-gaap**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing receivables that are equal to or greater than 90 days past due.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=6965416&loc=SL6953401-111524
+ Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue**Namespace Prefix:**us-gaap**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentPastDueLineItems**Namespace Prefix:**us-gaap**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |