Segment Reporting - Operations Reporting by Revenue (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Total revenue	$ 1,354	$ 1,097
Operating expenses, including leased vehicle expenses	633	425
Provision for loan losses	155	135
Interest expense	380	315
Equity income	28	0
Income before income taxes	214	222
Operating Segments [Member] | North America Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	906	636
Operating expenses, including leased vehicle expenses	487	274
Provision for loan losses	118	103
Interest expense	165	92
Equity income	0
Income before income taxes	136	167
Operating Segments [Member] | International Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	448	461
Operating expenses, including leased vehicle expenses	146	151
Provision for loan losses	37	32
Interest expense	206	214
Equity income	28
Income before income taxes	87	64
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	7	16
Operating expenses, including leased vehicle expenses	0	0
Provision for loan losses	0	0
Interest expense	16	25
Equity income	0
Income before income taxes	(9)	(9)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenue	(7)	(16)
Operating expenses, including leased vehicle expenses	0	0
Provision for loan losses	0	0
Interest expense	(7)	(16)
Equity income	0
Income before income taxes	$ 0	$ 0