Finance Receivables - Aging Analysis (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number Of Days After Which Finance Receivable Is Considered Past Due	any payment, including principal and interest, that is at least 31 days past the contractual due date
Number Of Days At Which Finance Receivables Are In Process Of Collection
Finance Receivables Aging Analysis [Abstract]
Financing Receivables	$ 89,878	$ 87,236	$ 87,045
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	13	17
Finance Receivables Aging Analysis [Abstract]
31-60 days past due	566	718
61-90 days past due	85	97
91-120 days past due	23	29
Greater than 120 days past due	39	52
Total past due	713	896
Current	55,194	53,200
Financing Receivables	55,907	54,096
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	1	3
Finance Receivables Aging Analysis [Abstract]
Total past due	110	117
Current	33,861	33,023
Financing Receivables	$ 33,971	$ 33,140