Segment Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) segment	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	4
Net financing revenue and other interest income	$ 1,693	$ 1,372
Other revenue	442	565
Total net revenue	2,135	1,937
Provision for credit losses	167	(13)
Total noninterest expense	1,122	943
Income from continuing operations before income tax expense	846	1,007
Total assets	184,297	181,879	$ 182,114
Net financing revenue and other interest income after the provision for credit losses	1,500	1,400
Operating Segments | Automotive Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	1,295	1,206
Other revenue	68	62
Total net revenue	1,363	1,268
Provision for credit losses	104	(22)
Total noninterest expense	534	487
Income from continuing operations before income tax expense	725	803
Total assets	105,754	101,566
Operating Segments | Insurance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	17	15
Other revenue	270	379
Total net revenue	287	394
Provision for credit losses	0	0
Total noninterest expense	274	253
Income from continuing operations before income tax expense	13	141
Total assets	9,220	9,221
Operating Segments | Mortgage Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	53	23
Other revenue	14	40
Total net revenue	67	63
Provision for credit losses	0	(4)
Total noninterest expense	56	44
Income from continuing operations before income tax expense	11	23
Total assets	18,596	12,923
Operating Segments | Corporate Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	83	71
Other revenue	24	26
Total net revenue	107	97
Provision for credit losses	6	13
Total noninterest expense	37	31
Income from continuing operations before income tax expense	64	53
Total assets	8,086	6,421
Corporate and Other
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	245	57
Other revenue	66	58
Total net revenue	311	115
Provision for credit losses	57	0
Total noninterest expense	221	128
Income from continuing operations before income tax expense	33	(13)
Total assets	$ 42,641	$ 51,748