Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		21 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Dec. 31, 2020
Allowance for loan losses
Beginning balance			$ 28,328	$ 13,123	$ 13,123
Gross charge-offs			3,596	5,365
Gross recoveries collected			(1,281)	(1,156)
Net charge-offs/(recoveries)			2,315	4,209
Provision for loan losses			(7,857)	17,724
Other			(6)	4
Ending balance	$ 18,150	$ 30,814	18,150	30,814	18,150
Allowance for lending-related commitments
Beginning balance			2,409	1,191	1,191
Provision for lending-related commitments			(106)	1,535
Other			2	(1)
Ending balance	2,305	2,823	2,305	2,823	2,305
Total allowance for credit losses	20,455	33,637	20,455	33,637	20,455	$ 30,800
Allowance for loan losses by impairment methodology
Asset-specific	169	1,672	169	1,672	169
Portfolio-based	17,981	29,142	17,981	29,142	17,981
Total allowance for loan losses	18,150	30,814	18,150	30,814	18,150	28,328
Loans by impairment methodology
Asset-specific	17,877	22,176	17,877	22,176	17,877
Portfolio-based	956,383	923,361	956,383	923,361	956,383
Total retained loans	974,260	945,537	974,260	945,537	974,260	960,506
Allowance for lending-related commitments by impairment methodology
Asset-specific	129	109	129	109	129
Portfolio-based	2,176	2,714	2,176	2,714	2,176
Total allowance for lending-related commitments	2,305	2,823	2,305	2,823	2,305	2,409
Lending-related commitments by impairment methodology
Asset-specific	641	607	641	607	641
Portfolio-based	494,367	451,854	494,367	451,854	494,367
Total lending-related commitments	495,008	452,461	495,008	452,461	495,008
Investment securities, allowance for credit losses	73	120	73	120	73	78
Collateral-dependent loans
Allowance for loan losses
Net charge-offs/(recoveries)			35	131
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	4,824	4,647	4,824	4,647	4,824
Cumulative effect of a change in accounting principle
Allowance for loan losses
Beginning balance				4,172	4,172
Allowance for lending-related commitments
Beginning balance				98	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			8,000
Consumer, excluding credit card
Allowance for loan losses
Beginning balance			3,636	2,538	2,538
Gross charge-offs			452	620
Gross recoveries collected			(470)	(483)
Net charge-offs/(recoveries)			(18)	137
Provision for loan losses			(1,778)	1,803
Other			(2)	1
Ending balance	1,874	4,502	1,874	4,502	1,874
Allowance for lending-related commitments
Beginning balance			187	12	12
Provision for lending-related commitments			(45)	71
Other			0	0
Ending balance	142	216	142	216	142
Total allowance for credit losses	2,016	4,718	2,016	4,718	2,016
Allowance for loan losses by impairment methodology
Asset-specific	(571)	228	(571)	228	(571)
Portfolio-based	2,445	4,274	2,445	4,274	2,445
Total allowance for loan losses	1,874	4,502	1,874	4,502	1,874	3,636
Loans by impairment methodology
Asset-specific	14,464	16,888	14,464	16,888	14,464
Portfolio-based	283,844	288,218	283,844	288,218	283,844
Total retained loans	298,308	305,106	298,308	305,106	298,308	302,127
Allowance for lending-related commitments by impairment methodology
Asset-specific	0	0	0	0	0
Portfolio-based	142	216	142	216	142
Total allowance for lending-related commitments	142	216	142	216	142	187
Lending-related commitments by impairment methodology
Asset-specific	0	0	0	0	0
Portfolio-based	36,819	35,587	36,819	35,587	36,819
Total lending-related commitments	36,819	35,587	36,819	35,587	36,819
Credit card lending-related commitments not permitted to have an allowance for credit losses	19,900	10,800	19,900	10,800	19,900
Consumer, excluding credit card | Collateral-dependent loans
Allowance for loan losses
Net charge-offs/(recoveries)			26	109
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	4,460	4,517	4,460	4,517	4,460
Consumer, excluding credit card | Cumulative effect of a change in accounting principle
Allowance for loan losses
Beginning balance				297	297
Allowance for lending-related commitments
Beginning balance				133	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	5,683
Gross charge-offs			2,957	4,104
Gross recoveries collected			(724)	(585)
Net charge-offs/(recoveries)			2,233	3,519
Provision for loan losses			(3,917)	10,119
Other			0	0
Ending balance	11,650	17,800	11,650	17,800	11,650
Allowance for lending-related commitments
Beginning balance			0	0	0
Provision for lending-related commitments			0	0
Other			0	0
Ending balance	0	0	0	0	0
Total allowance for credit losses	11,650	17,800	11,650	17,800	11,650
Allowance for loan losses by impairment methodology
Asset-specific	383	652	383	652	383
Portfolio-based	11,267	17,148	11,267	17,148	11,267
Total allowance for loan losses	11,650	17,800	11,650	17,800	11,650	17,800
Loans by impairment methodology
Asset-specific	1,083	1,432	1,083	1,432	1,083
Portfolio-based	142,083	138,158	142,083	138,158	142,083
Total retained loans	143,166	139,590	143,166	139,590	143,166
Allowance for lending-related commitments by impairment methodology
Asset-specific	0	0	0	0	0
Portfolio-based	0	0	0	0	0
Total allowance for lending-related commitments	0	0	0	0	0	0
Lending-related commitments by impairment methodology
Asset-specific	0	0	0	0	0
Portfolio-based	0	0	0	0	0
Total lending-related commitments	0	0	0	0	0
Credit card lending-related commitments not permitted to have an allowance for credit losses	710,600	662,900	710,600	662,900	710,600
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	0
Credit card | Cumulative effect of a change in accounting principle
Allowance for loan losses
Beginning balance				5,517	5,517
Allowance for lending-related commitments
Beginning balance				0	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	4,902
Gross charge-offs			187	641
Gross recoveries collected			(87)	(88)
Net charge-offs/(recoveries)	37	92	100	553
Provision for loan losses			(2,162)	5,802
Other			(4)	3
Ending balance	4,626	8,512	4,626	8,512	4,626
Allowance for lending-related commitments
Beginning balance			2,222	1,179	1,179
Provision for lending-related commitments			(61)	1,464
Other			2	(1)
Ending balance	2,163	2,607	2,163	2,607	2,163
Total allowance for credit losses	6,789	11,119	6,789	11,119	6,789
Allowance for loan losses by impairment methodology
Asset-specific	357	792	357	792	357
Portfolio-based	4,269	7,720	4,269	7,720	4,269
Total allowance for loan losses	4,626	8,512	4,626	8,512	4,626	6,892
Loans by impairment methodology
Asset-specific	2,330	3,856	2,330	3,856	2,330
Portfolio-based	530,456	496,985	530,456	496,985	530,456
Total retained loans	532,786	500,841	532,786	500,841	532,786	514,947
Allowance for lending-related commitments by impairment methodology
Asset-specific	129	109	129	109	129
Portfolio-based	2,034	2,498	2,034	2,498	2,034
Total allowance for lending-related commitments	2,163	2,607	2,163	2,607	2,163	$ 2,222
Lending-related commitments by impairment methodology
Asset-specific	641	607	641	607	641
Portfolio-based	457,548	416,267	457,548	416,267	457,548
Total lending-related commitments	458,189	416,874	458,189	416,874	458,189
Credit card lending-related commitments not permitted to have an allowance for credit losses	41,000	24,400	41,000	24,400	41,000
Decrease in allowance for credit losses			2,300
Wholesale | Collateral-dependent loans
Allowance for loan losses
Net charge-offs/(recoveries)			9	22
Collateral-dependent loans
Loans measured at fair value of collateral less cost to sell	$ 364	$ 130	$ 364	130	364
Wholesale | Cumulative effect of a change in accounting principle
Allowance for loan losses
Beginning balance				(1,642)	(1,642)
Allowance for lending-related commitments
Beginning balance				$ (35)	$ (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