Loans - Loan Portfolio Composition and Aging Analysis (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Current	$ 307,695	$ 302,305
Total	$ 320,472	$ 312,331
Current, percentage of total loans	96.01%	96.79%
Percentage of total loans	100.00%	100.00%
Unamortized premiums and discounts, deferred fees and costs	$ 1,400	$ 1,400
Credit Card:
Financing Receivable, Past Due [Line Items]
Current	147,412	132,961
Total	154,547	137,730
Consumer Banking:
Financing Receivable, Past Due [Line Items]
Current	70,097	74,985
Total	75,437	79,925
Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Current	68,768	73,467
Total	74,075	78,373
Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Current	1,329	1,518
Total	1,362	1,552
Commercial Banking:
Financing Receivable, Past Due [Line Items]
Current	90,186	94,359
Total	90,488	94,676
Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Current	34,325	37,417
Total	34,446	37,453
Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Current	55,861	56,942
Total	56,042	57,223
30-59 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 5,367	$ 4,666
Delinquent Loans, percentage of total loans	1.68%	1.50%
30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 2,084	$ 1,491
30-59 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	3,283	3,114
30-59 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	3,268	3,101
30-59 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	15	13
Total	15	13
30-59 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	0	61
30-59 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	0	0
30-59 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	0	61
60-89 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 3,119	$ 2,511
Delinquent Loans, percentage of total loans	0.97%	0.80%
60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 1,547	$ 1,033
60-89 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,558	1,422
60-89 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,555	1,418
60-89 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	3	4
Total	3	4
60-89 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	14	56
60-89 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	14	1
60-89 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	0	55
Greater than 90 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 4,291	$ 2,849
Delinquent Loans, percentage of total loans	1.34%	0.91%
Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 3,504	$ 2,245
Greater than 90 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	499	404
Greater than 90 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	484	387
Greater than 90 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	15	17
Total	15	17
Greater than 90 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	288	200
Greater than 90 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	107	35
Greater than 90 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	181	165
Total Delinquent Loans
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 12,777	$ 10,026
Total Delinquent Loans, percentage of total loans	3.99%	3.21%
Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 7,135	$ 4,769
Total Delinquent Loans | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	5,340	4,940
Total Delinquent Loans | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	5,307	4,906
Total Delinquent Loans | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	33	34
Total Delinquent Loans | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	302	317
Total Delinquent Loans | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	121	36
Total Delinquent Loans | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	181	281
Domestic credit card: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	140,860	127,066
Total	147,666	131,581
Domestic credit card: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,968	1,405
Total	1,968	1,405
Domestic credit card: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,471	975
Total	1,471	975
Domestic credit card: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	3,367	2,135
Total	3,367	2,135
Domestic credit card: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	6,806	4,515
International card businesses: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	6,552	5,895
Total	6,881	6,149
International card businesses: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	116	86
Total	116	86
International card businesses: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	76	58
Total	76	58
International card businesses: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	137	110
Total	137	110
International card businesses: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 329	$ 254