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
	Mar. 31, 2021	Mar. 31, 2020
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	$ 15,564
Provision (benefit) for credit losses	(823)	$ 5,423
Balance at the end of the period	14,017
Other
Allowance for Credit Losses [Roll Forward]
Provision (benefit) for credit losses	(2)	5
Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	15,564	7,208
Charge-offs	(1,354)	(2,457)
Recoveries	614	666
Net charge-offs	(740)	(1,791)
Provision (benefit) for credit losses	(813)	5,367
Allowance build (release) for credit losses	(1,553)	3,576
Other changes	6	(18)
Balance at the end of the period	14,017	14,073
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	195	135
Provision (benefit) for credit losses	(8)	51
Balance at the end of the period	187	223
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	14,204	14,296
Credit Card | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	11,191	5,395
Charge-offs	(993)	(1,849)
Recoveries	360	413
Net charge-offs	(633)	(1,436)
Provision (benefit) for credit losses	(492)	3,702
Allowance build (release) for credit losses	(1,125)	2,266
Other changes	6	(18)
Balance at the end of the period	10,072	10,346
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
Provision (benefit) for credit losses	0	0
Balance at the end of the period	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	10,072	10,346
Consumer Banking | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	2,715	1,038
Charge-offs	(342)	(496)
Recoveries	251	250
Net charge-offs	(91)	(246)
Provision (benefit) for credit losses	(126)	860
Allowance build (release) for credit losses	(217)	614
Other changes	0	0
Balance at the end of the period	2,498	2,154
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	5
Provision (benefit) for credit losses	0	0
Balance at the end of the period	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	2,498	2,154
Commercial Banking | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at the beginning of the period	1,658	775
Charge-offs	(19)	(112)
Recoveries	3	3
Net charge-offs	(16)	(109)
Provision (benefit) for credit losses	(195)	805
Allowance build (release) for credit losses	(211)	696
Other changes	0	0
Balance at the end of the period	1,447	1,573
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	195	130
Provision (benefit) for credit losses	(8)	51
Balance at the end of the period	187	223
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	$ 1,634	$ 1,796