Segment Reporting - Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Total revenue	$ 3,639	$ 3,488	$ 7,259	$ 6,899
Operating expenses	377	382	747	747
Leased vehicle expenses	1,637	1,684	3,451	3,471
Provision for loan losses	179	128	354	264
Interest expense	952	803	1,899	1,535
Equity income	42	45	87	97
Income before income taxes	536	536	895	979
North America Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	3,332	3,180	6,638	6,265
Operating expenses	281	276	557	547
Leased vehicle expenses	1,627	1,675	3,430	3,453
Provision for loan losses	142	90	281	187
Interest expense	831	685	1,654	1,282
Equity income	0	0	0	0
Income before income taxes	451	454	716	796
International Segment [Member]
Segment Reporting Information [Line Items]
Total revenue	307	308	621	634
Operating expenses	96	106	190	200
Leased vehicle expenses	10	9	21	18
Provision for loan losses	37	38	73	77
Interest expense	121	118	245	253
Equity income	42	45	87	97
Income before income taxes	$ 85	$ 82	$ 179	$ 183