Finance Receivables - Credit Quality (Details) - North America Segment [Member] - Automobile Loan [Member] - Retail Finance Receivables [Member] - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Finance receivables, net of fees	$ 26,969	$ 21,786
Finance receivables credit indicator, Percent	100.00%	100.00%
Prime - FICO Score 680 and greater [Member]
Financing Receivable, Recorded Investment [Line Items]
Finance receivables, net of fees	$ 12,332	$ 7,923
Finance receivables credit indicator, Percent	45.70%	36.40%
Near-prime - FICO Score 620 to 679 [Member]
Financing Receivable, Recorded Investment [Line Items]
Finance receivables, net of fees	$ 4,194	$ 3,468
Finance receivables credit indicator, Percent	15.60%	15.90%
Sub-prime - FICO Score less than 620 [Member]
Financing Receivable, Recorded Investment [Line Items]
Finance receivables, net of fees	$ 10,443	$ 10,395
Finance receivables credit indicator, Percent	38.70%	47.70%