Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) segment	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			4
Net financing revenue and other interest income	$ 1,764	$ 1,547	$ 3,457	$ 2,919
Other revenue	312	538	754	1,103
Total net revenue	2,076	2,085	4,211	4,022
Provision for credit losses	304	(32)	471	(45)
Total noninterest expense	1,138	1,075	2,260	2,018
Income from continuing operations before income tax expense	634	1,042	1,480	2,049
Total assets	185,703	180,470	185,703	180,470	$ 182,114
Net financing revenue and other interest income after the provision for credit losses	1,500	1,600	3,000	3,000
Operating Segments | Automotive Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	1,301	1,333	2,596	2,539
Other revenue	72	61	140	123
Total net revenue	1,373	1,394	2,736	2,662
Provision for credit losses	228	(23)	332	(45)
Total noninterest expense	545	500	1,079	987
Income from continuing operations before income tax expense	600	917	1,325	1,720
Total assets	107,178	100,162	107,178	100,162
Operating Segments | Insurance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	20	15	37	30
Other revenue	158	344	428	723
Total net revenue	178	359	465	753
Provision for credit losses	0	0	0	0
Total noninterest expense	300	272	574	525
Income from continuing operations before income tax expense	(122)	87	(109)	228
Total assets	8,819	9,394	8,819	9,394
Operating Segments | Mortgage Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	56	23	109	46
Other revenue	4	22	18	62
Total net revenue	60	45	127	108
Provision for credit losses	0	0	0	(4)
Total noninterest expense	54	45	110	89
Income from continuing operations before income tax expense	6	0	17	23
Total assets	19,126	13,865	19,126	13,865
Operating Segments | Corporate Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	77	77	160	148
Other revenue	19	33	43	59
Total net revenue	96	110	203	207
Provision for credit losses	8	(13)	14	0
Total noninterest expense	28	28	65	59
Income from continuing operations before income tax expense	60	95	124	148
Total assets	8,890	6,246	8,890	6,246
Corporate and Other
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	310	99	555	156
Other revenue	59	78	125	136
Total net revenue	369	177	680	292
Provision for credit losses	68	4	125	4
Total noninterest expense	211	230	432	358
Income from continuing operations before income tax expense	90	(57)	123	(70)
Total assets	$ 41,690	$ 50,803	$ 41,690	$ 50,803