Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) subsegment segment	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			4
Number of operating subsegments | subsegment			2
Net financing revenue and other interest income	$ 1,495	$ 1,573	$ 2,951	$ 3,175
Other revenue	505	506	1,035	1,004
Total net revenue	2,000	2,079	3,986	4,179
Provision for credit losses	457	427	964	873
Total noninterest expense	1,286	1,249	2,594	2,515
Income from continuing operations before income tax (benefit) expense	257	403	428	791
Total assets	192,531	197,241	192,531	197,241	$ 196,392
Net financing revenue and other interest income after the provision for credit losses	1,000	1,100	2,000	2,300
Operating Segments | Automotive Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	1,314	1,349	2,628	2,671
Other revenue	93	83	190	160
Total net revenue	1,407	1,432	2,818	2,831
Provision for credit losses	383	331	831	682
Total noninterest expense	617	600	1,258	1,206
Income from continuing operations before income tax (benefit) expense	407	501	729	943
Total assets	115,772	113,757	115,772	113,757
Operating Segments | Insurance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	30	29	59	55
Other revenue	338	337	722	718
Total net revenue	368	366	781	773
Provision for credit losses	0	0	0	0
Total noninterest expense	410	358	753	673
Income from continuing operations before income tax (benefit) expense	(42)	8	28	100
Total assets	9,174	8,890	9,174	8,890
Operating Segments | Mortgage Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	53	53	105	107
Other revenue	5	5	11	9
Total net revenue	58	58	116	116
Provision for credit losses	(1)	0	(1)	(1)
Total noninterest expense	32	37	65	75
Income from continuing operations before income tax (benefit) expense	27	21	52	42
Total assets	18,010	18,997	18,010	18,997
Operating Segments | Corporate Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	104	92	215	195
Other revenue	30	28	53	57
Total net revenue	134	120	268	252
Provision for credit losses	3	15	2	30
Total noninterest expense	33	33	78	78
Income from continuing operations before income tax (benefit) expense	98	72	188	144
Total assets	9,869	10,190	9,869	10,190
Corporate and Other
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	(6)	50	(56)	147
Other revenue	39	53	59	60
Total net revenue	33	103	3	207
Provision for credit losses	72	81	132	162
Total noninterest expense	194	221	440	483
Income from continuing operations before income tax (benefit) expense	(233)	(199)	(569)	(438)
Total assets	$ 39,706	$ 45,407	$ 39,706	$ 45,407