Segment Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) subsegment segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 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	$ 6,201	$ 6,850	$ 6,167
Other revenue	2,013	1,578	2,039
Total net revenue	8,214	8,428	8,206
Provision for credit losses	1,968	1,399	241
Total noninterest expense	5,163	4,687	4,110
Income (loss) from continuing operations before income tax expense	1,083	2,342	3,855
Total assets	196,392	191,826	182,114
Net financing revenue and other interest income after the provision for credit losses	4,200	5,500	5,900
Goodwill impairment	149	0	0
Operating Segments | Automotive Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	5,361	5,224	5,209
Other revenue	321	306	251
Total net revenue	5,682	5,530	5,460
Provision for credit losses	1,618	1,036	53
Total noninterest expense	2,450	2,244	2,023
Income (loss) from continuing operations before income tax expense	1,614	2,250	3,384
Total assets	115,387	111,463	103,653
Goodwill impairment	0
Operating Segments | Insurance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	117	89	59
Other revenue	1,428	1,023	1,345
Total net revenue	1,545	1,112	1,404
Provision for credit losses	0	0
Total noninterest expense	1,332	1,150	1,061
Income (loss) from continuing operations before income tax expense	213	(38)	343
Total assets	9,081	8,659	9,381
Goodwill impairment	0
Operating Segments | Mortgage Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	211	221	124
Other revenue	16	27	94
Total net revenue	227	248	218
Provision for credit losses	(3)	3	(1)
Total noninterest expense	138	190	187
Income (loss) from continuing operations before income tax expense	92	55	32
Total assets	18,512	19,529	17,847
Operating Segments | Corporate Finance operations
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	397	334	308
Other revenue	104	122	128
Total net revenue	501	456	436
Provision for credit losses	52	43	38
Total noninterest expense	142	131	116
Income (loss) from continuing operations before income tax expense	307	282	282
Total assets	11,212	10,544	7,950
Corporate and Other
Segment Reporting Information [Line Items]
Net financing revenue and other interest income	115	982	467
Other revenue	144	100	221
Total net revenue	259	1,082	688
Provision for credit losses	301	317	151
Total noninterest expense	1,101	972	723
Income (loss) from continuing operations before income tax expense	(1,143)	(207)	(186)
Total assets	42,200	$ 41,631	$ 43,283
Goodwill impairment	$ 149