Transfers of Receivables - Exposure Based on Fair Value of Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	$ 1,275	$ 1,256
Fair Value of Derivative Liabilities	251	400
Variable Interest Entity, Primary Beneficiary [Member]
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	47	4
Fair Value of Derivative Liabilities	60	134
Securitization Transactions [Member]
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	105	89
Fair Value of Derivative Liabilities	118	219
Securitization Transactions [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	47	4
Fair Value of Derivative Liabilities	60	134
Related to Variable Interest Entity - Not VIE [Member] | Securitization Transactions [Member]
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	52	74
Fair Value of Derivative Liabilities	47	63
Other, Not Variable Interest Entity Related [Member] | Securitization Transactions [Member]
Securitization Transactions [Line Items]
Fair Value of Derivative Assets	6	11
Fair Value of Derivative Liabilities	$ 11	$ 22