Consolidated Statement of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Revenue and Other Income [Abstract]
Interest and fees on finance receivables and loans	$ 6,581	$ 7,337	$ 6,688
Interest on loans held-for-sale	17	17	15
Interest and dividends on investment securities and other earning assets	736	955	788
Interest on cash and cash equivalents	28	78	72
Operating leases	1,435	1,470	1,489
Total financing revenue and other interest income	8,797	9,857	9,052
Interest Expense [Abstract]
Interest on deposits	1,952	2,538	1,735
Interest on short-term borrowings	42	135	149
Interest on long-term debt	1,249	1,570	1,753
Total interest expense	3,243	4,243	3,637
Net depreciation expense on operating lease assets	851	981	1,025
Net financing revenue and other interest income	4,703	4,633	4,390
Other revenue [Abstract]
Insurance premiums and service revenue earned	1,103	1,087	1,022
Gain on mortgage and automotive loans, net	110	28	25
Loss on Extinguishment of Debt	(102)	(2)	(1)
Other gain on investments, net	307	243	(50)
Other income, net of losses	565	405	418
Total other revenue	1,983	1,761	1,414
Total net revenue	6,686	6,394	5,804
Provision for credit losses	1,439	998	918
Noninterest Expense [Abstract]
Compensation and benefits expense	1,376	1,222	1,155
Insurance losses and loss adjustment expenses	363	321	295
Goodwill impairment	50	0	0
Other operating expenses	2,044	1,886	1,814
Total noninterest expense	3,833	3,429	3,264
Income from continuing operations before income tax expense	1,414	1,967	1,622
Statement [Abstract]
Income tax (benefit) expense from continuing operations	328	246	359
Net income from continuing operations	1,086	1,721	1,263
Loss from discontinued operations, net of tax	(1)	(6)	0
Net income	$ 1,085	$ 1,715	$ 1,263
Earnings Per Share, Basic [Abstract]
Net (loss) income from continuing operations, basic earnings per common share	$ 2.89	$ 4.38	$ 2.97
Loss from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	(0.02)	0
Net (loss) income, basic earnings per common share	2.89	4.36	2.97
Earnings Per Share, Diluted [Abstract]
Net (loss) income from continuing operations, diluted earnings per common share	2.88	4.35	2.95
Loss from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0	(0.02)	0
Net income, diluted earnings per common share	2.88	4.34	2.95
Cash dividends declared per common share	$ 0.76	$ 0.68	$ 0.56