Allowance for Credit Losses and Reserve for Unfunded Lending Commitments - Allowance for Credit Losses and Reserve for Unfunded Lending Commitments Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	$ 13,240
Provision (benefit) for credit losses	10,426	$ 5,847	$ (1,944)
Balance at the end of the period	15,296	13,240
Translation adjustment and purchase credit deteriorated loans	32	10	6
Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	13,240	11,430	15,564
Charge-offs	(10,702)	(6,064)	(4,740)
Recoveries	2,288	2,091	2,506
Net charge-offs	(8,414)	(3,973)	(2,234)
Provision (benefit) for credit losses	10,485	5,800	(1,912)
Allowance build (release) for credit losses	2,071	1,827	(4,146)
Other changes	48	(17)	12
Balance at the end of the period	15,296	13,240	11,430
Allowance for credit losses | Cumulative Effect, Period of Adoption, Adjustment
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	(63)
Balance at the end of the period		(63)
Allowance for credit losses | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	13,177
Balance at the end of the period		13,177
Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	218	165	195
Provision (benefit) for credit losses	(60)	53	(30)
Balance at the end of the period	158	218	165
Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	13,458	11,595
Balance at the end of the period	15,454	13,458	11,595
Credit Card: | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	9,545	8,345	11,191
Charge-offs	(7,787)	(4,362)	(3,481)
Recoveries	1,315	1,314	1,525
Net charge-offs	(6,472)	(3,048)	(1,956)
Provision (benefit) for credit losses	8,651	4,265	(902)
Allowance build (release) for credit losses	2,179	1,217	(2,858)
Other changes	48	(17)	12
Balance at the end of the period	11,709	9,545	8,345
Credit Card: | Allowance for credit losses | Cumulative Effect, Period of Adoption, Adjustment
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	(63)
Balance at the end of the period		(63)
Credit Card: | Allowance for credit losses | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	9,482
Balance at the end of the period		9,482
Credit Card: | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	0	0	0
Provision (benefit) for credit losses	0	0	0
Balance at the end of the period	0	0	0
Credit Card: | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	9,545	8,345
Balance at the end of the period	11,709	9,545	8,345
Consumer Banking: | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	2,237	1,918	2,715
Charge-offs	(2,327)	(1,614)	(1,211)
Recoveries	963	760	935
Net charge-offs	(1,364)	(854)	(276)
Provision (benefit) for credit losses	1,169	1,173	(521)
Allowance build (release) for credit losses	(195)	319	(797)
Other changes	0	0	0
Balance at the end of the period	2,042	2,237	1,918
Consumer Banking: | Allowance for credit losses | Cumulative Effect, Period of Adoption, Adjustment
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	0
Balance at the end 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 beginning of the period	2,237
Balance at the end of the period		2,237
Consumer Banking: | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	0	0	0
Provision (benefit) for credit losses	0	0	0
Balance at the end of the period	0	0	0
Consumer Banking: | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	2,237	1,918
Balance at the end of the period	2,042	2,237	1,918
Commercial Banking: | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	1,458	1,167	1,658
Charge-offs	(588)	(88)	(48)
Recoveries	10	17	46
Net charge-offs	(578)	(71)	(2)
Provision (benefit) for credit losses	665	362	(489)
Allowance build (release) for credit losses	87	291	(491)
Other changes	0	0	0
Balance at the end of the period	1,545	1,458	1,167
Commercial Banking: | Allowance for credit losses | Cumulative Effect, Period of Adoption, Adjustment
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	0
Balance at the end 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 beginning of the period	1,458
Balance at the end of the period		1,458
Commercial Banking: | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	218	165	195
Provision (benefit) for credit losses	(60)	53	(30)
Balance at the end of the period	158	218	165
Commercial Banking: | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at beginning of the period	1,676	1,332
Balance at the end of the period	$ 1,703	$ 1,676	$ 1,332