Finance Receivables - Aging Analysis (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
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	$ 100,686	$ 97,196	$ 86,812
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	16	16
Finance Receivables Aging Analysis [Abstract]
Total past due	759	881
Current	60,195	59,068
Financing Receivables	60,954	59,949	53,531
Consumer Portfolio Segment [Member] | 31-60 Days Past Due [Member]
Finance Receivables Aging Analysis [Abstract]
Total past due	611	708
Consumer Portfolio Segment [Member] | 61-90 Days Past Due [Member]
Finance Receivables Aging Analysis [Abstract]
Total past due	81	108
Consumer Portfolio Segment [Member] | 91-120 Days Past Due [Member]
Finance Receivables Aging Analysis [Abstract]
Total past due	27	27
Consumer Portfolio Segment [Member] | Greater Than 120 Days Past Due [Member]
Finance Receivables Aging Analysis [Abstract]
Total past due	40	38
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	1	1
Finance Receivables Aging Analysis [Abstract]
Total past due	104	116
Current	39,628	37,131
Financing Receivables	$ 39,732	$ 37,247	$ 33,281