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	3 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		$ 15,564
Provision (benefit) for credit losses		(1,944)	$ 10,264	$ 6,236
Balance at the end of the period		11,430	15,564
Financing Receivable Allowance for credit loss Translation Adjustments and Purchase Credit Deteriorated Loans		6
Other
Allowance for Credit Losses [Roll Forward]
Provision (benefit) for credit losses		(2)	3	0
Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		15,564	7,208	7,220
Charge-offs		(4,740)	(7,677)	(8,809)
Recoveries		2,506	2,452	2,557
Net charge-offs		(2,234)	(5,225)	(6,252)
Provision (benefit) for credit losses		(1,912)	10,238	6,223
Allowance build (release) for credit losses		(4,146)	5,013	(29)
Other changes		12	36	17
Balance at the end of the period		11,400	15,564	7,208
Allowance for credit losses | Other comprehensive income before reclassifications
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance			10,515
Balance at the end of the period				10,515
Allowance for credit loss				2,845
Allowance for credit losses | Finance charge and fee reserve reclassification
Allowance for Credit Losses [Roll Forward]
Allowance for credit loss				462
Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		195	135	122
Provision (benefit) for credit losses		(30)	23	13
Balance at the end of the period		165	195	135
Reserve for unfunded lending commitments | Other comprehensive income before reclassifications
Allowance for Credit Losses [Roll Forward]
Allowance for credit loss				37
Reserve for unfunded lending commitments | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance			172
Balance at the end of the period				172
Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		15,759	7,343
Balance at the end of the period		11,595	15,759	7,343
Credit Card | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		11,191	5,395	5,535
Charge-offs		(3,481)	(5,749)	(6,711)
Recoveries		1,525	1,479	1,562
Net charge-offs		(1,956)	(4,270)	(5,149)
Provision (benefit) for credit losses		(902)	7,327	4,992
Allowance build (release) for credit losses	$ 327	(2,858)	3,057	(157)
Other changes		12	36	17
Balance at the end of the period			11,191	5,395
Credit Card | Allowance for credit losses | Other comprehensive income before reclassifications
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance			8,098
Balance at the end of the period				8,098
Allowance for credit loss				2,241
Credit Card | Allowance for credit losses | Finance charge and fee reserve reclassification
Allowance for Credit Losses [Roll Forward]
Allowance for credit loss				462
Credit Card | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		0	0	0
Provision (benefit) for credit losses		0	0	0
Balance at the end of the period		0	0	0
Credit Card | Reserve for unfunded lending commitments | Other comprehensive income before reclassifications
Allowance for Credit Losses [Roll Forward]
Allowance for credit loss				0
Credit Card | Reserve for unfunded lending commitments | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance			0
Balance at the end of the period				0
Credit Card | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		11,191	5,395
Balance at the end of the period		8,345	11,191	5,395
Consumer Banking | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		2,715	1,038	1,048
Charge-offs		(1,211)	(1,534)	(1,917)
Recoveries		935	956	970
Net charge-offs		(276)	(578)	(947)
Provision (benefit) for credit losses		(521)	1,753	937
Allowance build (release) for credit losses		(797)	1,175	(10)
Other changes		0	0	0
Balance at the end of the period			2,715	1,038
Consumer Banking | Allowance for credit losses | Other comprehensive income before reclassifications
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance			1,540
Balance at the end of the period				1,540
Allowance for credit loss				502
Consumer Banking | Allowance for credit losses | Finance charge and fee reserve reclassification
Allowance for Credit Losses [Roll Forward]
Allowance for credit loss				0
Consumer Banking | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		0	5	4
Provision (benefit) for credit losses		0	0	1
Balance at the end of the period		0	0	5
Consumer Banking | Reserve for unfunded lending commitments | Other comprehensive income before reclassifications
Allowance for Credit Losses [Roll Forward]
Allowance for credit loss				(5)
Consumer Banking | Reserve for unfunded lending commitments | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance			0
Balance at the end of the period				0
Consumer Banking | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		2,715	1,043
Balance at the end of the period		1,918	2,715	1,043
Commercial Banking | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		1,658	775	637
Charge-offs		(48)	(394)	(181)
Recoveries		46	17	25
Net charge-offs		(2)	(377)	(156)
Provision (benefit) for credit losses		(489)	1,158	294
Allowance build (release) for credit losses		(491)	781	138
Other changes		0	0	0
Balance at the end of the period			1,658	775
Commercial Banking | Allowance for credit losses | Other comprehensive income before reclassifications
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance			877
Balance at the end of the period				877
Allowance for credit loss				102
Commercial Banking | Allowance for credit losses | Finance charge and fee reserve reclassification
Allowance for Credit Losses [Roll Forward]
Allowance for credit loss				0
Commercial Banking | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		195	130	118
Provision (benefit) for credit losses		(30)	23	12
Balance at the end of the period		165	195	130
Commercial Banking | Reserve for unfunded lending commitments | Other comprehensive income before reclassifications
Allowance for Credit Losses [Roll Forward]
Allowance for credit loss				42
Commercial Banking | Reserve for unfunded lending commitments | Cumulative Effect, Period of Adoption, Adjusted Balance
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance			172
Balance at the end of the period				172
Commercial Banking | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance		1,853	905
Balance at the end of the period		$ 1,332	$ 1,853	$ 905