Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($) subsegment segment	Mar. 31, 2023 USD ($)	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	$ 1,456	$ 1,602
Other revenue	530	498
Total net revenue	1,986	2,100
Provision for credit losses	507	446
Total noninterest expense	1,308	1,266
Income (loss) from continuing operations before income tax expense	171	388
Total assets	192,877	196,165	$ 196,392
Net financing revenue and other interest income after the provision for credit losses	949	1,200
Operating Segments | Automotive Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	1,314	1,322
Other revenue	97	77
Total net revenue	1,411	1,399
Provision for credit losses	448	351
Total noninterest expense	641	606
Income (loss) from continuing operations before income tax expense	322	442
Total assets	114,613	111,960
Operating Segments | Insurance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	29	26
Other revenue	384	381
Total net revenue	413	407
Provision for credit losses	0	0
Total noninterest expense	343	315
Income (loss) from continuing operations before income tax expense	70	92
Total assets	9,100	8,867
Operating Segments | Mortgage Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	52	54
Other revenue	6	4
Total net revenue	58	58
Provision for credit losses	0	(1)
Total noninterest expense	33	38
Income (loss) from continuing operations before income tax expense	25	21
Total assets	18,303	19,290
Operating Segments | Corporate Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	111	103
Other revenue	23	29
Total net revenue	134	132
Provision for credit losses	(1)	15
Total noninterest expense	45	45
Income (loss) from continuing operations before income tax expense	90	72
Total assets	10,410	10,226
Corporate and Other
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	(50)	97
Other revenue	20	7
Total net revenue	(30)	104
Provision for credit losses	60	81
Total noninterest expense	246	262
Income (loss) from continuing operations before income tax expense	(336)	(239)
Total assets	$ 40,451	$ 45,822