Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Financing Revenue and Other Income [Abstract]
Interest and fees on finance receivables and loans	$ 1,630	$ 1,860	$ 3,372	$ 3,667
Interest on loans held-for-sale	4	3	6	5
Interest and dividends on investment securities and other earning assets	197	244	423	484
Interest on cash and cash equivalents	4	21	18	44
Operating leases	343	363	710	724
Total financing revenue and other interest income	2,178	2,491	4,529	4,924
Interest Expense [Abstract]
Interest on deposits	541	651	1,133	1,243
Interest on short-term borrowings	13	37	30	81
Interest on long-term debt	318	407	666	826
Total interest expense	872	1,095	1,829	2,150
Net depreciation expense on operating lease assets	252	239	500	485
Net financing revenue and other interest income	1,054	1,157	2,200	2,289
Other revenue [Abstract]
Insurance premiums and service revenue earned	263	261	540	522
Gain on mortgage and automotive loans, net	14	2	2	12
Other gain on investments, net	188	39	109	147
Other income, net of losses	90	93	170	180
Total other revenue	555	395	821	861
Total net revenue	1,609	1,552	3,021	3,150
Provision for credit losses	287	177	1,190	459
Noninterest Expense [Abstract]
Compensation and benefits expense	334	296	694	614
Insurance losses and loss adjustment expenses	142	127	216	186
Goodwill impairment	50	0	50	0
Other operating expenses	459	458	945	911
Total noninterest expense	985	881	1,905	1,711
Income (loss) from continuing operations before income tax expense (benefit)	337	494	(74)	980
Statement [Abstract]
Income tax expense (benefit) from continuing operations	95	(90)	3	21
Net income (loss) from continuing operations	242	584	(77)	959
Loss from discontinued operations, net of tax	(1)	(2)	(1)	(3)
Net income (loss)	241	582	(78)	956
Other comprehensive income, net of tax	109	309	692	615
Comprehensive Income	$ 350	$ 891	$ 614	$ 1,571
Earnings Per Share, Basic [Abstract]
Net income (loss) from continuing operations, basic earnings per common share	$ 0.65	$ 1.47	$ (0.20)	$ 2.39
Loss from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	0	0	(0.01)
Net income (loss), basic earnings per common share	0.64	1.46	(0.21)	2.39
Earnings Per Share, Diluted [Abstract]
Net income (loss) from continuing operations, diluted earnings per common share	0.64	1.46	(0.20)	2.38
Loss from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0	0	0	(0.01)
Net income (loss), diluted earnings per common share	0.64	1.46	(0.21)	2.37
Cash dividends declared per common share	$ 0.19	$ 0.17	$ 0.38	$ 0.34