Segment Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) subsegment segment	Sep. 30, 2022 USD ($)	Dec. 31, 2022 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	$ 1,533	$ 1,719	$ 4,708	$ 5,176
Other revenue (loss)	435	297	1,439	1,051
Total net revenue	1,968	2,016	6,147	6,227
Provision for credit losses	508	438	1,381	909
Total noninterest expense	1,232	1,161	3,747	3,421
Income (loss) from continuing operations before income tax (benefit) expense	228	417	1,019	1,897
Total assets	195,704	188,640	195,704	188,640	$ 191,826
Net financing revenue and other interest income after the provision for credit losses	1,000	1,300	3,300	4,300
Operating Segments | Automotive Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	1,360	1,303	4,031	3,899
Other revenue (loss)	79	74	239	214
Total net revenue	1,439	1,377	4,270	4,113
Provision for credit losses	444	328	1,126	660
Total noninterest expense	618	561	1,824	1,640
Income (loss) from continuing operations before income tax (benefit) expense	377	488	1,320	1,813
Total assets	114,742	109,114	114,742	109,114
Operating Segments | Insurance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	29	24	84	61
Other revenue (loss)	293	236	1,011	664
Total net revenue	322	260	1,095	725
Provision for credit losses	0	0	0	0
Total noninterest expense	338	290	1,011	864
Income (loss) from continuing operations before income tax (benefit) expense	(16)	(30)	84	(139)
Total assets	8,736	8,533	8,736	8,533
Operating Segments | Mortgage Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	53	57	160	166
Other revenue (loss)	4	7	13	25
Total net revenue	57	64	173	191
Provision for credit losses	(2)	2	(3)	2
Total noninterest expense	33	43	108	153
Income (loss) from continuing operations before income tax (benefit) expense	26	19	68	36
Total assets	18,745	19,862	18,745	19,862
Operating Segments | Corporate Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	97	80	292	240
Other revenue (loss)	24	54	81	97
Total net revenue	121	134	373	337
Provision for credit losses	5	13	35	27
Total noninterest expense	32	30	110	95
Income (loss) from continuing operations before income tax (benefit) expense	84	91	228	215
Total assets	10,749	9,840	10,749	9,840
Corporate and Other
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	(6)	255	141	810
Other revenue (loss)	35	(74)	95	51
Total net revenue	29	181	236	861
Provision for credit losses	61	95	223	220
Total noninterest expense	211	237	694	669
Income (loss) from continuing operations before income tax (benefit) expense	(243)	(151)	(681)	(28)
Total assets	$ 42,732	$ 41,291	$ 42,732	$ 41,291