Segment Reporting - Operations Reporting by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Total revenue	$ 1,515	$ 1,191	$ 2,869	$ 2,288
Operating expenses, including leased vehicle expenses	786	459	1,419	884
Provision for loan losses	141	113	296	248
Interest expense	391	354	771	669
Equity income	28	0	56	0
Income before income taxes	225	265	439	487
Operating Segments [Member] | North America Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	1,085	691	1,991	1,327
Operating expenses, including leased vehicle expenses	648	310	1,135	584
Provision for loan losses	111	90	229	193
Interest expense	193	104	358	196
Equity income	0		0
Income before income taxes	133	187	269	354
Operating Segments [Member] | International Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	430	500	878	961
Operating expenses, including leased vehicle expenses	138	149	284	300
Provision for loan losses	30	23	67	55
Interest expense	183	248	389	462
Equity income	28		56
Income before income taxes	107	80	194	144
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	4	15	11	31
Operating expenses, including leased vehicle expenses	0	0	0	0
Provision for loan losses	0	0	0	0
Interest expense	19	17	35	42
Equity income	0		0
Income before income taxes	(15)	(2)	(24)	(11)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenue	(4)	(15)	(11)	(31)
Operating expenses, including leased vehicle expenses	0	0	0	0
Provision for loan losses	0	0	0	0
Interest expense	(4)	(15)	(11)	(31)
Equity income	0		0
Income before income taxes	$ 0	$ 0	$ 0	$ 0