Segment Reporting and Geographic Information - Operations Reporting by Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total revenue	$ 3,636	$ 3,659	$ 3,639	$ 3,620	$ 3,599	$ 3,518	$ 3,488	$ 3,411	$ 14,554	$ 14,016	$ 12,151
Operating expenses									1,564	1,522	1,390
Leased vehicle expenses									6,685	6,917	6,415
Provision for loan losses (Note 3)									726	642	757
Interest expense									3,641	3,225	2,566
Equity income									166	183	173
Income from continuing operations before income taxes	$ 498	$ 711	$ 536	$ 359	$ 416	$ 498	$ 536	$ 443	2,104	1,893	1,196
North America [Member]
Segment Reporting Information [Line Items]
Total revenue									13,318	12,771	10,999
Operating expenses									1,172	1,125	1,050
Leased vehicle expenses									6,634	6,879	6,391
Provision for loan losses (Note 3)									569	490	623
Interest expense									3,171	2,735	2,032
Equity income									0	0	0
Income from continuing operations before income taxes									1,772	1,542	903
International [Member]
Segment Reporting Information [Line Items]
Total revenue									1,236	1,245	1,152
Operating expenses									392	397	340
Leased vehicle expenses									51	38	24
Provision for loan losses (Note 3)									157	152	134
Interest expense									470	490	534
Equity income									166	183	173
Income from continuing operations before income taxes									$ 332	$ 351	$ 293