Segment Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) segment	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments | segment			4
Net financing revenue and other interest income	$ 1,719	$ 1,594	$ 5,176	$ 4,513
Other revenue	297	391	1,051	1,494
Total net revenue	2,016	1,985	6,227	6,007
Provision for credit losses	438	76	909	31
Total noninterest expense	1,161	1,002	3,421	3,020
Income from continuing operations before income tax expense	417	907	1,897	2,956
Total assets	188,640	179,184	188,640	179,184	$ 182,114
Net financing revenue and other interest income after the provision for credit losses	1,300	1,500	4,300	4,500
Automotive Finance operations
Segment Reporting Information [Line Items]
Other revenue	74	61	214	184
Insurance operations
Segment Reporting Information [Line Items]
Other revenue	236	283	664	1,006
Mortgage Finance operations
Segment Reporting Information [Line Items]
Other revenue	7	19	25	81
Corporate Finance operations
Segment Reporting Information [Line Items]
Other revenue	54	16	97	75
Operating Segments | Automotive Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	1,303	1,329	3,899	3,868
Other revenue	74	61	214	184
Total net revenue	1,377	1,390	4,113	4,052
Provision for credit losses	328	53	660	8
Total noninterest expense	561	512	1,640	1,499
Income from continuing operations before income tax expense	488	825	1,813	2,545
Total assets	109,114	99,617	109,114	99,617
Operating Segments | Insurance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	24	14	61	44
Other revenue	236	283	664	1,006
Total net revenue	260	297	725	1,050
Provision for credit losses	0	0	0	0
Total noninterest expense	290	273	864	798
Income from continuing operations before income tax expense	(30)	24	(139)	252
Total assets	8,533	9,354	8,533	9,354
Operating Segments | Mortgage Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	57	36	166	82
Other revenue	7	19	25	81
Total net revenue	64	55	191	163
Provision for credit losses	2	2	2	(2)
Total noninterest expense	43	47	153	136
Income from continuing operations before income tax expense	19	6	36	29
Total assets	19,862	16,328	19,862	16,328
Operating Segments | Corporate Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	80	77	240	225
Other revenue	54	16	97	75
Total net revenue	134	93	337	300
Provision for credit losses	13	5	27	5
Total noninterest expense	30	27	95	86
Income from continuing operations before income tax expense	91	61	215	209
Total assets	9,840	6,729	9,840	6,729
Corporate and Other
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	255	138	810	294
Other revenue	(74)	12	51	148
Total net revenue	181	150	861	442
Provision for credit losses	95	16	220	20
Total noninterest expense	237	143	669	501
Income from continuing operations before income tax expense	(151)	(9)	(28)	(79)
Total assets	$ 41,291	$ 47,156	$ 41,291	$ 47,156