Allowance for Credit Losses and Reserve for Unfunded Lending Commitments - Allowance for Loan and Lease Losses and Reserve for Unfunded Lending Commitments Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period			$ 15,564
Provision (benefit) for credit losses	$ (1,160)	$ 4,246	(1,983)	$ 9,669
Balance at the end of the period	12,346		12,346
Other
Allowance for Credit Losses [Roll Forward]
Provision (benefit) for credit losses	0	(1)	(2)	4
Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	14,017	14,073	15,564	7,208
Charge-offs	(1,235)	(2,131)	(2,589)	(4,588)
Recoveries	694	626	1,308	1,292
Net charge-offs	(541)	(1,505)	(1,281)	(3,296)
Provision (benefit) for credit losses	(1,137)	4,252	(1,950)	9,619
Allowance build (release) for credit losses	(1,678)	2,747	(3,231)	6,323
Other changes	7	12	13	(6)
Balance at the end of the period	12,346	16,832	12,346	16,832
Allowance for credit losses | Cumulative effects from adoption of new accounting standards
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				2,845
Allowance for credit losses | Finance charge and fee reserve reclassification
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				462
Allowance for credit losses | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				10,515
Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	187	223	195	135
Provision (benefit) for credit losses	(23)	(5)	(31)	46
Balance at the end of the period	164	218	164	218
Reserve for unfunded lending commitments | Cumulative effects from adoption of new accounting standards
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				37
Reserve for unfunded lending commitments | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				172
Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	12,510	17,050	12,510	17,050
Credit Card | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	10,072	10,346	11,191	5,395
Charge-offs	(967)	(1,612)	(1,960)	(3,461)
Recoveries	396	401	756	814
Net charge-offs	(571)	(1,211)	(1,204)	(2,647)
Provision (benefit) for credit losses	(635)	2,944	(1,127)	6,646
Allowance build (release) for credit losses	(1,206)	1,733	(2,331)	3,999
Other changes	7	12	13	(6)
Balance at the end of the period	8,873	12,091	8,873	12,091
Credit Card | Allowance for credit losses | Cumulative effects from adoption of new accounting standards
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				2,241
Credit Card | Allowance for credit losses | Finance charge and fee reserve reclassification
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				462
Credit Card | Allowance for credit losses | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				8,098
Credit Card | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	0	0	0	0
Provision (benefit) for credit losses	0	0	0	0
Balance at the end of the period	0	0	0	0
Credit Card | Reserve for unfunded lending commitments | Cumulative effects from adoption of new accounting standards
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				0
Credit Card | Reserve for unfunded lending commitments | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				0
Credit Card | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	8,873	12,091	8,873	12,091
Consumer Banking | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	2,498	2,154	2,715	1,038
Charge-offs	(260)	(416)	(602)	(912)
Recoveries	271	224	522	474
Net charge-offs	11	(192)	(80)	(438)
Provision (benefit) for credit losses	(306)	876	(432)	1,736
Allowance build (release) for credit losses	(295)	684	(512)	1,298
Other changes	0	0	0	0
Balance at the end of the period	2,203	2,838	2,203	2,838
Consumer Banking | Allowance for credit losses | Cumulative effects from adoption of new accounting standards
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				502
Consumer Banking | Allowance for credit losses | Finance charge and fee reserve reclassification
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				0
Consumer Banking | Allowance for credit losses | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				1,540
Consumer Banking | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	0	0	0	5
Provision (benefit) for credit losses	0	0	0	0
Balance at the end of the period	0	0	0	0
Consumer Banking | Reserve for unfunded lending commitments | Cumulative effects from adoption of new accounting standards
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				(5)
Consumer Banking | Reserve for unfunded lending commitments | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				0
Consumer Banking | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	2,203	2,838	2,203	2,838
Commercial Banking | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	1,447	1,573	1,658	775
Charge-offs	(8)	(103)	(27)	(215)
Recoveries	27	1	30	4
Net charge-offs	19	(102)	3	(211)
Provision (benefit) for credit losses	(196)	432	(391)	1,237
Allowance build (release) for credit losses	(177)	330	(388)	1,026
Other changes	0	0	0	0
Balance at the end of the period	1,270	1,903	1,270	1,903
Commercial Banking | Allowance for credit losses | Cumulative effects from adoption of new accounting standards
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				102
Commercial Banking | Allowance for credit losses | Finance charge and fee reserve reclassification
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				0
Commercial Banking | Allowance for credit losses | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				877
Commercial Banking | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	187	223	195	130
Provision (benefit) for credit losses	(23)	(5)	(31)	46
Balance at the end of the period	164	218	164	218
Commercial Banking | Reserve for unfunded lending commitments | Cumulative effects from adoption of new accounting standards
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				42
Commercial Banking | Reserve for unfunded lending commitments | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period				172
Commercial Banking | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	$ 1,434	$ 2,121	$ 1,434	$ 2,121