Segment Reporting - Schedule of Operations Reporting by Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting Information [Line Items]
Revenues	$ 4,337	$ 4,031	$ 12,755	$ 11,760
Costs and expenses
(Gain) loss on termination of leased vehicles			494	605
Provision for loan losses	244	298	926	676
Interest expense	1,651	1,550	4,886	4,431
Equity income	9	10	37	55
Income before income taxes	804	687	2,193	2,246
Reportable Segments
Segment Reporting Information [Line Items]
Revenues	4,322	4,025	12,720	11,748
Costs and expenses
Income before income taxes	824	700	2,244	2,284
North America
Segment Reporting Information [Line Items]
Revenues	3,901	3,661	11,531	10,603
Costs and expenses
Salaries and benefits	258	251	781	748
Leased vehicle depreciation	1,216	1,190	3,616	3,577
(Gain) loss on termination of leased vehicles	(148)	(188)	(495)	(606)
Provision for loan losses	202	277	808	598
Interest expense	1,464	1,385	4,350	3,930
GM Protection claim losses	17	8	39	20
Other segment items	140	116	413	334
Equity income	0	0	0	0
Income before income taxes	753	623	2,018	2,003
International
Segment Reporting Information [Line Items]
Revenues	421	364	1,189	1,145
Costs and expenses
Salaries and benefits	40	37	116	114
Leased vehicle depreciation	22	18	60	56
(Gain) loss on termination of leased vehicles	2	0	2	0
Provision for loan losses	42	21	118	77
Interest expense	187	165	536	502
GM Protection claim losses	0	0	0	0
Other segment items	67	56	168	170
Equity income	9	10	37	55
Income before income taxes	71	77	227	281
Other Operating Segment
Segment Reporting Information [Line Items]
Revenues	14	6	35	12
Costs and expenses
Income before income taxes	$ (20)	$ (13)	$ (52)	$ (38)