| **Allowance for Doubtful Accounts - Impaired Finance Receivables (Details) (USD $)In Millions, unless otherwise specified** | 12 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| Impaired Financing Receivable, Related Allowance                                                                            | $ 9             | $ 10 |
| Financing Receivable, Recorded Investment, Nonaccrual Status                                                                | 10              | 14 |
| Impaired finance receivables with specific loss reserves [Domain]                                                           |            |   |
| Impaired Financing Receivable, Recorded Investment                                                                          | 14              | 15 |
| Impaired financing receivable without specific loss reserves [Domain]                                                       |            |   |
| Impaired Financing Receivable, Recorded Investment                                                                          | 1               | 2 |
| Retail Portfolio [Member]                                                                                                   |            |   |
| Impaired Financing Receivable, Related Allowance                                                                            | 9               | 10 |
| Financing Receivable, Recorded Investment, Nonaccrual Status                                                                | 10              | 14 |
| Impaired Financing Receivable, Average Recorded Investment                                                                  | 16              | 32 |
| Retail Portfolio [Member] | Impaired finance receivables with specific loss reserves [Domain]                               |            |   |
| Impaired Financing Receivable, Recorded Investment                                                                          | 14              | 15 |
| Retail Portfolio [Member] | Impaired financing receivable without specific loss reserves [Domain]                           |            |   |
| Impaired Financing Receivable, Recorded Investment                                                                          | 1               | 2 |
| Wholesale Portfolio [Member]                                                                                                |            |   |
| Impaired Financing Receivable, Related Allowance                                                                            | 0               | 0 |
| Financing Receivable, Recorded Investment, Nonaccrual Status                                                                | 0               | 0 |
| Wholesale Portfolio [Member] | Impaired finance receivables with specific loss reserves [Domain]                            |            |   |
| Impaired Financing Receivable, Recorded Investment                                                                          | 0               | 0 |
| Wholesale Portfolio [Member] | Impaired financing receivable without specific loss reserves [Domain]                        |            |   |
| Impaired Financing Receivable, Recorded Investment                                                                          | $ 0             | $ 0 |

| 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=7512638&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=7512638&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=7512638&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=7512638&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=7512638&loc=d3e5212-111524
+ Details**Name:**us-gaap_ImpairedFinancingReceivableRelatedAllowance**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |