Finance Receivables - Delinquency (Details) - Retail Finance Receivables [Member] - Automobile Loan [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
In repossession	$ 51	$ 46
In repossession of contractual amount due (percent)	0.10%	0.20%
Financing receivable and in repossession past due	$ 1,828	$ 1,764
Financing receivable and in repossession past due (percent)	5.50%	6.00%
31 to 60 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable past due	$ 1,235	$ 1,237
Financing receivable past due (percent)	3.70%	4.20%
Greater Than 60 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable past due	$ 542	$ 481
Financing receivable past due (percent)	1.70%	1.60%
30 or More Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing receivable past due	$ 1,777	$ 1,718
Financing receivable past due (percent)	5.40%	5.80%