| **Allowance for Doubtful Accounts - Impaired Finance Receivables (Details) (USD $)In Millions, unless otherwise specified**                                                                                                                                                                                                                                                                                              | 12 Months Ended |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| Retail Portfolio [Member]                                                                                                                                                                                                                                                                                                                                                                                                |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Impaired Financing Receivable, Average Recorded Investment                                                                                                                                                                                                                                                                                                                                                               | $ 13            |  | $ 16 |  |
| Impaired finance receivables with specific loss reserves [Member]                                                                                                                                                                                                                                                                                                                                                        |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Impaired Financing Receivable, Recorded Investment                                                                                                                                                                                                                                                                                                                                                                       | 15              | [1] | 14 | [1] |
| Impaired finance receivables with specific loss reserves [Member] | Retail Portfolio [Member]                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Impaired Financing Receivable, Recorded Investment                                                                                                                                                                                                                                                                                                                                                                       | 15              |  | 14 |  |
| Impaired finance receivables with specific loss reserves [Member] | Wholesale Portfolio [Member]                                                                                                                                                                                                                                                                                                                         |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Impaired Financing Receivable, Recorded Investment                                                                                                                                                                                                                                                                                                                                                                       | 0               |  | 0 |  |
| Impaired financing receivable without specific loss reserves [Member]                                                                                                                                                                                                                                                                                                                                                    |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Impaired Financing Receivable, Recorded Investment                                                                                                                                                                                                                                                                                                                                                                       | 1               |  | 1 |  |
| Impaired financing receivable without specific loss reserves [Member] | Retail Portfolio [Member]                                                                                                                                                                                                                                                                                                                        |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Impaired Financing Receivable, Recorded Investment                                                                                                                                                                                                                                                                                                                                                                       | 1               |  | 1 |  |
| Impaired financing receivable without specific loss reserves [Member] | Wholesale Portfolio [Member]                                                                                                                                                                                                                                                                                                                     |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Impaired Financing Receivable, Recorded Investment                                                                                                                                                                                                                                                                                                                                                                       | 0               |  | 0 |  |
| Specific loss reserves on impaired finance receivables [Member]                                                                                                                                                                                                                                                                                                                                                          |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Specific loss reserves on impaired finance receivables                                                                                                                                                                                                                                                                                                                                                                   | 6               |  | 9 |  |
| Specific loss reserves on impaired finance receivables [Member] | Retail Portfolio [Member]                                                                                                                                                                                                                                                                                                                              |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Specific loss reserves on impaired finance receivables                                                                                                                                                                                                                                                                                                                                                                   | 6               |  | 9 |  |
| Specific loss reserves on impaired finance receivables [Member] | Wholesale Portfolio [Member]                                                                                                                                                                                                                                                                                                                           |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Specific loss reserves on impaired finance receivables                                                                                                                                                                                                                                                                                                                                                                   | 0               |  | 0 |  |
| Finance receivable non-accrual status [Member]                                                                                                                                                                                                                                                                                                                                                                           |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Finance receivables on non-accrual status                                                                                                                                                                                                                                                                                                                                                                                | 10              |  | 10 |  |
| Finance receivable non-accrual status [Member] | Retail Portfolio [Member]                                                                                                                                                                                                                                                                                                                                               |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Finance receivables on non-accrual status                                                                                                                                                                                                                                                                                                                                                                                | 10              |  | 10 |  |
| Finance receivable non-accrual status [Member] | Wholesale Portfolio [Member]                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| **Finance Receivable, Impaired [Line Items]**                                                                                                                                                                                                                                                                                                                                                                            |            |  |   |  |
| Finance receivables on non-accrual status                                                                                                                                                                                                                                                                                                                                                                                | $ 0             |  | $ 0 |  |
|                                                                                                                                                                                                                                                                                                                                                                                                                          |
| [1]Certain impaired finance receivables are measured at fair value on a nonrecurring basis. An impairment charge is recorded for the amount by which the carrying value of the receivables exceeds the fair value of the underlying collateral, net of remarketing costs. Fair values of the underlying collateral are determined by reference to dealer vehicle value publications adjusted for certain market factors. |

| X                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5111-111524
+ Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| 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=28368275&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=28368275&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 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 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953550-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableRecordedInvestment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of allowance for credit losses related to recorded investment.
+ 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 (a)(3) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524
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