Segment Reporting - Operations Reporting by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Total revenue	$ 2,990	$ 2,138	$ 5,738	$ 4,069
Operating expenses	333	296	663	569
Leased vehicle expenses	1,549	1,062	2,978	1,951
Provision for loan losses	158	144	369	334
Interest expense	635	460	1,231	882
Equity income	41	37	88	73
Income from continuing operations before income taxes	356	213	585	406
Operating Segments [Member] | North America Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	2,700	1,886	5,174	3,574
Operating expenses	253	215	501	416
Leased vehicle expenses	1,543	1,061	2,969	1,949
Provision for loan losses	133	125	320	302
Interest expense	497	337	952	642
Equity income	0	0	0	0
Income from continuing operations before income taxes	274	148	432	265
Operating Segments [Member] | International Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	290	252	564	495
Operating expenses	80	81	162	153
Leased vehicle expenses	6	1	9	2
Provision for loan losses	25	19	49	32
Interest expense	138	123	279	240
Equity income	41	37	88	73
Income from continuing operations before income taxes	$ 82	$ 65	$ 153	$ 141