Segment Reporting and Geographic Information - Operations Reporting by Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total revenue	$ 2,692	$ 2,499	$ 2,292	$ 2,075	$ 1,878	$ 1,707	$ 1,515	$ 1,354	$ 9,558	$ 6,454	$ 4,854
Operating expenses									1,490	1,293	1,162
Leased vehicle expenses									4,529	2,200	847
Provision for loan losses									669	624	604
Interest expense									2,108	1,616	1,426
Equity income									151	116	0
Income before income taxes	$ 194	$ 228	$ 266	$ 225	$ 167	$ 231	$ 225	$ 214	913	837	815
Operating Segments [Member] | North America [Member]
Segment Reporting Information [Line Items]
Total revenue									7,948	4,777	2,909
Operating expenses									891	735	542
Leased vehicle expenses									4,499	2,190	843
Provision for loan losses									566	466	472
Interest expense									1,481	833	459
Equity income									0	0
Income before income taxes									511	553	593
Operating Segments [Member] | International [Member]
Segment Reporting Information [Line Items]
Total revenue									1,610	1,677	1,945
Operating expenses									599	558	620
Leased vehicle expenses									30	10	4
Provision for loan losses									103	158	132
Interest expense									626	722	954
Equity income									151	116
Income before income taxes									403	345	235
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Total revenue									(1)	13	56
Operating expenses									0	0	0
Leased vehicle expenses									0	0	0
Provision for loan losses									0	0	0
Interest expense									0	74	69
Equity income									0	0
Income before income taxes									(1)	(61)	(13)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenue									1	(13)	(56)
Operating expenses									0	0	0
Leased vehicle expenses									0	0	0
Provision for loan losses									0	0	0
Interest expense									1	(13)	(56)
Equity income									0	0
Income before income taxes									$ 0	$ 0	$ 0