Transfers of Receivables - Financial Performance Related to Securitizations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Securitization Transactions [Line Items]
Interest expense	$ 663	$ 691	$ 2,002	$ 2,056
Securitization Transactions [Member]
Securitization Transactions [Line Items]
Interest expense	149	157	444	488
Securitization Transactions [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Securitization Transactions [Line Items]
Interest expense	125	138	377	434
Securitization Transactions [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Securitization Transactions [Line Items]
Interest expense	$ 24	$ 19	$ 67	$ 54