Transfers of Receivables - Financial Performance Related to Securitizations (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Securitization Transactions [Line Items]
Interest expense	$ 666	$ 683
Securitization Transactions [Member]
Securitization Transactions [Line Items]
Interest expense	147	168
Securitization Transactions [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Securitization Transactions [Line Items]
Interest expense	126	151
Securitization Transactions [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Securitization Transactions [Line Items]
Interest expense	$ 21	$ 17