Finance Receivables - Delinquency (Details) - Retail Finance Receivables [Member] - Automobile Loan [Member] - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
In repossession	$ 51	$ 46
In repossession (percent)	0.20%	0.20%
Financing receivable and in repossession past due	$ 1,586	$ 1,560
Financing receivable and in repossession past due (percent)	5.10%	5.40%
31 to 60 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable past due	$ 1,070	$ 1,062
Financing receivable past due (percent)	3.40%	3.60%
Greater Than 60 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable past due	$ 465	$ 452
Financing receivable past due (percent)	1.50%	1.60%
Thirty or More Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable past due	$ 1,535	$ 1,514
Financing receivable past due (percent)	4.90%	5.20%