Business Segments and Revenue from Contracts with Customers - Segment Results and Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net interest income (loss)	$ 5,743	$ 5,460	$ 11,565	$ 11,485
Non-interest income (loss)	1,631	1,096	2,922	2,320
Total net revenue (loss)	7,374	6,556	14,487	13,805
Provision (benefit) for credit losses	(1,160)	4,246	(1,983)	9,669
Non-interest expense	3,966	3,770	7,706	7,499
Income (loss) from continuing operations before income taxes	4,568	(1,460)	8,764	(3,363)
Income tax provision (benefit)	1,031	(543)	1,900	(1,106)
Income (loss) from continuing operations, net of tax	3,537	(917)	6,864	(2,257)
Income (loss) from continuing operations before income taxes	249,597	251,512	249,597	251,512	$ 251,624
Total Deposits	306,308	304,238	306,308	304,238	$ 305,442
Uncollectible portion of billed finance charges and fees	175	318	355	707
Operating segments | Credit Card
Segment Reporting Information [Line Items]
Net interest income (loss)	3,217	3,369	6,589	7,071
Non-interest income (loss)	1,253	845	2,282	1,756
Total net revenue (loss)	4,470	4,214	8,871	8,827
Provision (benefit) for credit losses	(635)	2,944	(1,127)	6,646
Non-interest expense	2,263	1,969	4,398	4,177
Income (loss) from continuing operations before income taxes	2,842	(699)	5,600	(1,996)
Income tax provision (benefit)	672	(166)	1,325	(472)
Income (loss) from continuing operations, net of tax	2,170	(533)	4,275	(1,524)
Income (loss) from continuing operations before income taxes	101,017	107,310	101,017	107,310
Total Deposits	0	0	0	0
Operating segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income (loss)	2,101	1,665	4,131	3,322
Non-interest income (loss)	144	97	285	223
Total net revenue (loss)	2,245	1,762	4,416	3,545
Provision (benefit) for credit losses	(306)	876	(432)	1,736
Non-interest expense	1,123	1,036	2,240	2,027
Income (loss) from continuing operations before income taxes	1,428	(150)	2,608	(218)
Income tax provision (benefit)	337	(36)	615	(52)
Income (loss) from continuing operations, net of tax	1,091	(114)	1,993	(166)
Income (loss) from continuing operations before income taxes	74,759	66,712	74,759	66,712
Total Deposits	251,155	246,804	251,155	246,804
Operating segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income (loss)	460	518	980	1,009
Non-interest income (loss)	257	180	497	418
Total net revenue (loss)	717	698	1,477	1,427
Provision (benefit) for credit losses	(219)	427	(422)	1,283
Non-interest expense	417	425	836	837
Income (loss) from continuing operations before income taxes	519	(154)	1,063	(693)
Income tax provision (benefit)	123	(36)	251	(164)
Income (loss) from continuing operations, net of tax	396	(118)	812	(529)
Income (loss) from continuing operations before income taxes	73,821	77,490	73,821	77,490
Total Deposits	42,973	35,669	42,973	35,669
Other
Segment Reporting Information [Line Items]
Net interest income (loss)	(35)	(92)	(135)	83
Non-interest income (loss)	(23)	(26)	(142)	(77)
Total net revenue (loss)	(58)	(118)	(277)	6
Provision (benefit) for credit losses	0	(1)	(2)	4
Non-interest expense	163	340	232	458
Income (loss) from continuing operations before income taxes	(221)	(457)	(507)	(456)
Income tax provision (benefit)	(101)	(305)	(291)	(418)
Income (loss) from continuing operations, net of tax	(120)	(152)	(216)	(38)
Income (loss) from continuing operations before income taxes	0	0	0	0
Total Deposits	$ 12,180	$ 21,765	$ 12,180	$ 21,765