Business Segments and Revenue from Contracts with Customers - Segment Results and Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net interest income (loss)	$ 5,822	$ 6,025
Non-interest income (loss)	1,291	1,224
Total net revenue (loss)	7,113	7,249
Provision (benefit) for credit losses	(823)	5,423
Non-interest expense	3,740	3,729
Income (loss) from continuing operations before income taxes	4,196	(1,903)
Income tax provision	869	(563)
Income (loss) from continuing operations, net of tax	3,327	(1,340)
Income (loss) from continuing operations before income taxes	243,131	262,990	$ 251,624
Total Deposits	310,328	269,689	$ 305,442
Uncollectible portion of billed finance charges and fees	180	389
Operating segments | Credit Card
Segment Reporting Information [Line Items]
Net interest income (loss)	3,372	3,702
Non-interest income (loss)	1,029	911
Total net revenue (loss)	4,401	4,613
Provision (benefit) for credit losses	(492)	3,702
Non-interest expense	2,135	2,208
Income (loss) from continuing operations before income taxes	2,758	(1,297)
Income tax provision	653	(306)
Income (loss) from continuing operations, net of tax	2,105	(991)
Income (loss) from continuing operations before income taxes	99,127	117,797
Total Deposits	0	0
Operating segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income (loss)	2,030	1,657
Non-interest income (loss)	141	126
Total net revenue (loss)	2,171	1,783
Provision (benefit) for credit losses	(126)	860
Non-interest expense	1,117	991
Income (loss) from continuing operations before income taxes	1,180	(68)
Income tax provision	278	(16)
Income (loss) from continuing operations, net of tax	902	(52)
Income (loss) from continuing operations before income taxes	70,202	64,033
Total Deposits	254,001	217,607
Operating segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income (loss)	520	491
Non-interest income (loss)	240	238
Total net revenue (loss)	760	729
Provision (benefit) for credit losses	(203)	856
Non-interest expense	419	412
Income (loss) from continuing operations before income taxes	544	(539)
Income tax provision	128	(128)
Income (loss) from continuing operations, net of tax	416	(411)
Income (loss) from continuing operations before income taxes	73,802	81,160
Total Deposits	41,552	32,822
Other
Segment Reporting Information [Line Items]
Net interest income (loss)	(100)	175
Non-interest income (loss)	(119)	(51)
Total net revenue (loss)	(219)	124
Provision (benefit) for credit losses	(2)	5
Non-interest expense	69	118
Income (loss) from continuing operations before income taxes	(286)	1
Income tax provision	(190)	(113)
Income (loss) from continuing operations, net of tax	(96)	114
Income (loss) from continuing operations before income taxes	0	0
Total Deposits	$ 14,775	$ 19,260