Allowance for Credit Losses (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
Allowance for loan losses
Beginning balance			$ 28,328	$ 13,123
Gross charge-offs			2,656	3,779
Gross recoveries collected			(865)	(750)
Net charge-offs/(recoveries)			1,791	3,029
Provision for loan losses			(7,038)	17,324
Other			1	1
Ending balance	$ 19,500	$ 31,591	19,500	31,591
Allowance for lending-related commitments
Beginning balance			2,409	1,191
Provision for lending-related commitments			588	1,421
Other			1	0
Ending balance	2,998	2,710	2,998	2,710
Total allowance for credit losses	22,498	34,301	22,498	34,301
Allowance for loan losses by impairment methodology
Asset-specific	374	1,662	374	1,662
Portfolio-based	19,126	29,929	19,126	29,929
Total allowance for loan losses	19,500	31,591	19,500	31,591	$ 28,328
Loans by impairment methodology
Asset-specific	19,377	22,020	19,377	22,020
Portfolio-based	944,288	943,428	944,288	943,428
Total retained loans	963,665	965,448	963,665	965,448	960,506
Allowance for lending-related commitments by impairment methodology
Asset-specific	150	115	150	115
Portfolio-based	2,848	2,595	2,848	2,595
Total allowance for lending-related commitments	2,998	2,710	2,998	2,710	2,409
Lending-related commitments by impairment methodology
Asset-specific	851	762	851	762
Portfolio-based	495,170	426,538	495,170	426,538
Total lending-related commitments	496,021	427,300	496,021	427,300
Investment securities, allowance for credit losses	87	23	87	23	78
Collateral-dependent loans
Allowance for loan losses
Net charge-offs/(recoveries)			29	78
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	5,030	3,671	5,030	3,671
Cumulative effect of a change in accounting principle
Allowance for loan losses
Beginning balance				4,172
Allowance for lending-related commitments
Beginning balance				98
Allowance for loan losses by impairment methodology
Total allowance for loan losses
Allowance for lending-related commitments by impairment methodology
Total allowance for lending-related commitments
Consumer-related
Lending-related commitments by impairment methodology
Decrease in allowance for credit losses			7,100
Consumer, excluding credit card
Allowance for loan losses
Beginning balance			3,636	2,538
Gross charge-offs			308	425
Gross recoveries collected			(318)	(348)
Net charge-offs/(recoveries)			(10)	77
Provision for loan losses			(1,746)	2,115
Other			(2)	(1)
Ending balance	1,898	4,872	1,898	4,872
Allowance for lending-related commitments
Beginning balance			187	12
Provision for lending-related commitments			(46)	95
Other			1	1
Ending balance	142	241	142	241
Total allowance for credit losses	2,040	5,113	2,040	5,113
Allowance for loan losses by impairment methodology
Asset-specific	(557)	263	(557)	263
Portfolio-based	2,455	4,609	2,455	4,609
Total allowance for loan losses	1,898	4,872	1,898	4,872	3,636
Loans by impairment methodology
Asset-specific	15,187	16,749	15,187	16,749
Portfolio-based	282,544	290,256	282,544	290,256
Total retained loans	297,731	307,005	297,731	307,005	302,127
Allowance for lending-related commitments by impairment methodology
Asset-specific	0	0	0	0
Portfolio-based	142	241	142	241
Total allowance for lending-related commitments	142	241	142	241	187
Lending-related commitments by impairment methodology
Asset-specific	0	0	0	0
Portfolio-based	36,092	35,417	36,092	35,417
Total lending-related commitments	36,092	35,417	36,092	35,417
Credit card lending-related commitments not permitted to have an allowance for credit losses	20,800	9,900	20,800	9,900
Consumer, excluding credit card | Collateral-dependent loans
Allowance for loan losses
Net charge-offs/(recoveries)			23	56
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	4,689	3,505	4,689	3,505
Consumer, excluding credit card | Cumulative effect of a change in accounting principle
Allowance for loan losses
Beginning balance				297
Allowance for lending-related commitments
Beginning balance				133
Allowance for loan losses by impairment methodology
Total allowance for loan losses
Allowance for lending-related commitments by impairment methodology
Total allowance for lending-related commitments
Credit card
Allowance for loan losses
Beginning balance			17,800	5,683
Gross charge-offs			2,213	2,863
Gross recoveries collected			(475)	(372)
Net charge-offs/(recoveries)			1,738	2,491
Provision for loan losses			(3,562)	9,091
Other			0	0
Ending balance	12,500	17,800	12,500	17,800
Allowance for lending-related commitments
Beginning balance			0	0
Provision for lending-related commitments			0	0
Other			0	0
Ending balance	0	0	0	0
Total allowance for credit losses	12,500	17,800	12,500	17,800
Allowance for loan losses by impairment methodology
Asset-specific	443	642	443	642
Portfolio-based	12,057	17,158	12,057	17,158
Total allowance for loan losses	12,500	17,800	12,500	17,800	17,800
Loans by impairment methodology
Asset-specific	1,180	1,422	1,180	1,422
Portfolio-based	139,899	140,234	139,899	140,234
Total retained loans	141,079	141,656	141,079	141,656
Allowance for lending-related commitments by impairment methodology
Asset-specific	0	0	0	0
Portfolio-based	0	0	0	0
Total allowance for lending-related commitments	0	0	0	0	0
Lending-related commitments by impairment methodology
Asset-specific	0	0	0	0
Portfolio-based	0	0	0	0
Total lending-related commitments	0	0	0	0
Credit card lending-related commitments not permitted to have an allowance for credit losses	682,500	673,800	682,500	673,800
Credit card | Collateral-dependent loans
Allowance for loan losses
Net charge-offs/(recoveries)			0	0
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	0	0	0	0
Credit card | Cumulative effect of a change in accounting principle
Allowance for loan losses
Beginning balance				5,517
Allowance for lending-related commitments
Beginning balance				0
Allowance for loan losses by impairment methodology
Total allowance for loan losses
Allowance for lending-related commitments by impairment methodology
Total allowance for lending-related commitments
Wholesale
Allowance for loan losses
Beginning balance			6,892	4,902
Gross charge-offs			135	491
Gross recoveries collected			(72)	(30)
Net charge-offs/(recoveries)	10	299	63	461
Provision for loan losses			(1,730)	6,118
Other			3	2
Ending balance	5,102	8,919	5,102	8,919
Allowance for lending-related commitments
Beginning balance			2,222	1,179
Provision for lending-related commitments			634	1,326
Other			0	(1)
Ending balance	2,856	2,469	2,856	2,469
Total allowance for credit losses	7,958	11,388	7,958	11,388
Allowance for loan losses by impairment methodology
Asset-specific	488	757	488	757
Portfolio-based	4,614	8,162	4,614	8,162
Total allowance for loan losses	5,102	8,919	5,102	8,919	6,892
Loans by impairment methodology
Asset-specific	3,010	3,849	3,010	3,849
Portfolio-based	521,845	512,938	521,845	512,938
Total retained loans	524,855	516,787	524,855	516,787	514,947
Allowance for lending-related commitments by impairment methodology
Asset-specific	150	115	150	115
Portfolio-based	2,706	2,354	2,706	2,354
Total allowance for lending-related commitments	2,856	2,469	2,856	2,469	$ 2,222
Lending-related commitments by impairment methodology
Asset-specific	851	762	851	762
Portfolio-based	459,078	391,121	459,078	391,121
Total lending-related commitments	459,929	391,883	459,929	391,883
Credit card lending-related commitments not permitted to have an allowance for credit losses	42,700	21,500	42,700	21,500
Decrease in allowance for credit losses			1,100
Wholesale | Collateral-dependent loans
Allowance for loan losses
Net charge-offs/(recoveries)			6	22
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	$ 341	$ 166	$ 341	166
Wholesale | Cumulative effect of a change in accounting principle
Allowance for loan losses
Beginning balance				(1,642)
Allowance for lending-related commitments
Beginning balance				$ (35)
Allowance for loan losses by impairment methodology
Total allowance for loan losses
Allowance for lending-related commitments by impairment methodology
Total allowance for lending-related commitments