Consolidated Statement of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Financing Revenue and Other Income [Abstract]
Interest and fees on finance receivables and loans	$ 1,602	$ 1,859	$ 4,974	$ 5,526
Interest on loans held-for-sale	5	8	11	13
Interest and dividends on investment securities and other earning assets	173	237	596	721
Interest on cash and cash equivalents	5	19	23	63
Operating leases	360	368	1,070	1,092
Total financing revenue and other interest income	2,145	2,491	6,674	7,415
Interest Expense [Abstract]
Interest on deposits	452	658	1,585	1,901
Interest on short-term borrowings	9	33	39	114
Interest on long-term debt	309	378	975	1,204
Total interest expense	770	1,069	2,599	3,219
Net depreciation expense on operating lease assets	175	234	675	719
Net financing revenue and other interest income	1,200	1,188	3,400	3,477
Other revenue [Abstract]
Insurance premiums and service revenue earned	276	280	816	802
Gain on mortgage and automotive loans, net	33	10	35	22
Gain (Loss) on Extinguishment of Debt	(49)	1	(50)	(2)
Other gain on investments, net	64	27	173	174
Other income, net of losses	160	95	331	278
Total other revenue	484	413	1,305	1,274
Total net revenue	1,684	1,601	4,705	4,751
Provision for credit losses	147	263	1,337	722
Noninterest Expense [Abstract]
Compensation and benefits expense	342	296	1,036	910
Insurance losses and loss adjustment expenses	85	74	301	260
Goodwill impairment	0	0	50	0
Other operating expenses	478	468	1,423	1,379
Total noninterest expense	905	838	2,810	2,549
Income from continuing operations before income tax expense	632	500	558	1,480
Statement [Abstract]
Income tax expense from continuing operations	156	119	159	140
Net income from continuing operations	476	381	399	1,340
Loss from discontinued operations, net of tax	0	0	(1)	(3)
Net income	476	381	398	1,337
Other comprehensive income, net of tax	(120)	106	572	721
Comprehensive Income	$ 356	$ 487	$ 970	$ 2,058
Earnings Per Share, Basic [Abstract]
Net income from continuing operations, basic earnings per common share	$ 1.27	$ 0.98	$ 1.06	$ 3.37
Loss from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	0	0	(0.01)
Net income, basic earnings per common share	1.27	0.97	1.06	3.36
Earnings Per Share, Diluted [Abstract]
Net income from continuing operations, diluted earnings per common share	1.26	0.97	1.06	3.35
Loss from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0	0	0	(0.01)
Net income, diluted earnings per common share	1.26	0.97	1.06	3.35
Cash dividends declared per common share	$ 0.19	$ 0.17	$ 0.57	$ 0.51