Segment Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment	4
Net financing revenue and other interest income	$ 6,167	$ 4,703	$ 4,633
Other revenue	2,039	1,983	1,761
Total net revenue	8,206	6,686	6,394
Provision for credit losses	241	1,439	998
Total noninterest expense	4,110	3,833	3,429
Income from continuing operations before income tax expense	3,855	1,414	1,967
Total assets	182,114	182,165	180,644
Net financing revenue and other interest income after the provision for credit losses	5,900	3,300	3,600
Operating Segments | Automotive Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	5,209	4,284	4,141
Other revenue	251	204	249
Total net revenue	5,460	4,488	4,390
Provision for credit losses	53	1,236	962
Total noninterest expense	2,023	1,967	1,810
Income from continuing operations before income tax expense	3,384	1,285	1,618
Total assets	103,653	104,794	113,863
Operating Segments | Insurance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	59	42	54
Other revenue	1,345	1,334	1,274
Total net revenue	1,404	1,376	1,328
Provision for credit losses	0	0	0
Total noninterest expense	1,061	1,092	1,013
Income from continuing operations before income tax expense	343	284	315
Total assets	9,381	9,137	8,547
Operating Segments | Mortgage Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	124	118	171
Other revenue	94	102	22
Total net revenue	218	220	193
Provision for credit losses	(1)	7	5
Total noninterest expense	187	160	148
Income from continuing operations before income tax expense	32	53	40
Total assets	17,847	14,889	16,279
Operating Segments | Corporate Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	308	299	239
Other revenue	128	45	45
Total net revenue	436	344	284
Provision for credit losses	38	149	36
Total noninterest expense	116	107	95
Income from continuing operations before income tax expense	282	88	153
Total assets	7,950	6,108	5,787
Corporate and Other
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	467	(40)	28
Other revenue	221	298	171
Total net revenue	688	258	199
Provision for credit losses	151	47	(5)
Total noninterest expense	723	507	363
Income from continuing operations before income tax expense	(186)	(296)	(159)
Total assets	$ 43,283	$ 47,237	$ 36,168