Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) subsegment segment	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			3
Number of operating subsegments | subsegment			2
Total financing revenue and other interest income	$ 3,325	$ 3,538	$ 6,718	$ 7,120
Total interest expense	1,593	1,866	3,268	3,788
Net depreciation expense on operating lease assets	216	155	456	347
Net financing revenue and other interest income	1,516	1,517	2,994	2,985
Other revenue	566	505	629	1,035
Total net revenue	2,082	2,022	3,623	4,020
Provision for credit losses	384	457	575	964
Compensation and benefits expense	430	442	935	961
Insurance losses and loss adjustment expenses	203	181	364	293
Goodwill impairment	0	0	305	0	$ 118
Other operating expenses
Technology and communications	101	103	204	209
Other	528	560	1,088	1,131
Total other operating expenses	629	663	1,292	1,340
Total noninterest expense	1,262	1,286	2,896	2,594
Income from continuing operations before income tax expense	436	279	152	462
Total assets	189,473	192,379	189,473	192,379	191,836
Net financing revenue and other interest income after the provision for credit losses	1,100	1,100	2,400	2,000
Operating Segments | Automotive Finance operations
Segment Reporting Information [Line Items]
Total financing revenue and other interest income	2,603	2,606	5,174	5,182
Total interest expense	1,093	1,065	2,158	2,075
Net depreciation expense on operating lease assets	216	155	456	347
Net financing revenue and other interest income	1,294	1,386	2,560	2,760
Other revenue	97	93	194	190
Total net revenue	1,391	1,479	2,754	2,950
Provision for credit losses	387	383	821	831
Compensation and benefits expense	166	160	349	338
Insurance losses and loss adjustment expenses	0	0	0	0
Goodwill impairment			0		0
Other operating expenses
Technology and communications	30	31	59	63
Other	336	321	678	654
Total other operating expenses	366	352	737	717
Total noninterest expense	532	512	1,086	1,055
Income from continuing operations before income tax expense	472	584	847	1,064
Total assets	111,709	115,524	111,709	115,524
Operating Segments | Insurance operations
Segment Reporting Information [Line Items]
Total financing revenue and other interest income	45	41	89	80
Total interest expense	15	14	29	27
Net depreciation expense on operating lease assets	0	0	0	0
Net financing revenue and other interest income	30	27	60	53
Other revenue	422	338	786	722
Total net revenue	452	365	846	775
Provision for credit losses	0	0	0	0
Compensation and benefits expense	26	26	56	54
Insurance losses and loss adjustment expenses	203	181	364	293
Goodwill impairment			0		0
Other operating expenses
Technology and communications	4	4	9	9
Other	191	194	387	389
Total other operating expenses	195	198	396	398
Total noninterest expense	424	405	816	745
Income from continuing operations before income tax expense	28	(40)	30	30
Total assets	9,705	9,174	9,705	9,174
Operating Segments | Corporate Finance operations
Segment Reporting Information [Line Items]
Total financing revenue and other interest income	233	252	454	521
Total interest expense	125	140	242	289
Net depreciation expense on operating lease assets	0	0	0	0
Net financing revenue and other interest income	108	112	212	232
Other revenue	19	30	48	53
Total net revenue	127	142	260	285
Provision for credit losses	(2)	3	12	2
Compensation and benefits expense	19	17	44	44
Insurance losses and loss adjustment expenses	0	0	0	0
Goodwill impairment			0
Other operating expenses
Technology and communications	1	2	2	3
Other	13	11	30	27
Total other operating expenses	14	13	32	30
Total noninterest expense	33	30	76	74
Income from continuing operations before income tax expense	96	109	172	209
Total assets	11,040	9,869	11,040	9,869
Corporate and Other
Segment Reporting Information [Line Items]
Total financing revenue and other interest income	444	639	1,001	1,337
Total interest expense	360	647	839	1,397
Net depreciation expense on operating lease assets	0	0	0	0
Net financing revenue and other interest income	84	(8)	162	(60)
Other revenue	28	44	(399)	70
Total net revenue	112	36	(237)	10
Provision for credit losses	(1)	71	(258)	131
Compensation and benefits expense	219	239	486	525
Insurance losses and loss adjustment expenses	0	0	0	0
Goodwill impairment			305		$ 118
Other operating expenses
Technology and communications	66	66	134	134
Other	(12)	34	(7)	61
Total other operating expenses	54	100	127	195
Total noninterest expense	273	339	918	720
Income from continuing operations before income tax expense	(160)	(374)	(897)	(841)
Total assets	$ 57,019	$ 57,812	$ 57,019	$ 57,812