Finance Receivables - Delinquency (Details) - Retail Finance Receivables [Member] - Automobile Loan [Member] - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
In repossession	$ 60	$ 53
In repossession (percent)	0.20%	0.20%
Financing receivable and in repossession past due	$ 1,690	$ 1,644
Financing receivable and in repossession past due (percent)	5.20%	5.80%
31 to 60 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable past due	$ 1,127	$ 1,137
Financing receivable past due (percent)	3.50%	4.00%
Greater Than 60 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable past due	$ 503	$ 454
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	$ 1,630	$ 1,591
Financing receivable past due (percent)	5.00%	5.60%