Finance Receivables - Aging Analysis (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Sep. 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	90 days
Finance Receivables Aging Analysis [Abstract]
Financing Receivables	$ 93,036	$ 87,236	$ 85,522
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	15	17
Finance Receivables Aging Analysis [Abstract]
31-60 days past due	597	718
61-90 days past due	94	97
91-120 days past due	25	29
Greater than 120 days past due	39	52
Total past due	755	896
Current	58,369	53,200
Financing Receivables	59,124	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	3	3
Finance Receivables Aging Analysis [Abstract]
Total past due	127	117
Current	33,785	33,023
Financing Receivables	$ 33,912	$ 33,140