Loans - Loan Portfolio Composition and Aging Analysis (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Current	$ 303,105	$ 302,305
Total	$ 314,780	$ 312,331
Current, percentage of total loans	96.29%	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	140,437	132,961
Total	146,783	137,730
Consumer Banking:
Financing Receivable, Past Due [Line Items]
Current	72,022	74,985
Total	76,844	79,925
Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Current	70,665	73,467
Total	75,456	78,373
Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Current	1,357	1,518
Total	1,388	1,552
Commercial Portfolio
Financing Receivable, Past Due [Line Items]
Current	90,646	94,359
Total	91,153	94,676
Commercial Portfolio | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Current	35,324	37,417
Total	35,622	37,453
Commercial Portfolio | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Current	55,322	56,942
Total	$ 55,531	$ 57,223
30-59 days
Financing Receivable, Past Due [Line Items]
Past due, percentage of total loans	1.60%	1.50%
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 5,032	$ 4,666
30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	1,925	1,491
30-59 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	2,976	3,114
30-59 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	2,961	3,101
30-59 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Total	15	13
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	15	13
30-59 days | Commercial Portfolio
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	131	61
30-59 days | Commercial Portfolio | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	126	0
30-59 days | Commercial Portfolio | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 5	$ 61
60-89 days
Financing Receivable, Past Due [Line Items]
Past due, percentage of total loans	0.90%	0.80%
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 2,845	$ 2,511
60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	1,396	1,033
60-89 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	1,412	1,422
60-89 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	1,409	1,418
60-89 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Total	3	4
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	3	4
60-89 days | Commercial Portfolio
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	37	56
60-89 days | Commercial Portfolio | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	37	1
60-89 days | Commercial Portfolio | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 0	$ 55
Greater than 90 days
Financing Receivable, Past Due [Line Items]
Past due, percentage of total loans	1.21%	0.91%
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 3,798	$ 2,849
Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	3,025	2,245
Greater than 90 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	434	404
Greater than 90 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	421	387
Greater than 90 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Total	13	17
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	13	17
Greater than 90 days | Commercial Portfolio
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	339	200
Greater than 90 days | Commercial Portfolio | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	135	35
Greater than 90 days | Commercial Portfolio | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 204	$ 165
Total Delinquent Loans
Financing Receivable, Past Due [Line Items]
Past due total, percentage of total loans	3.71%	3.21%
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 11,675	$ 10,026
Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	6,346	4,769
Total Delinquent Loans | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	4,822	4,940
Total Delinquent Loans | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	4,791	4,906
Total Delinquent Loans | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	31	34
Total Delinquent Loans | Commercial Portfolio
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	507	317
Total Delinquent Loans | Commercial Portfolio | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	298	36
Total Delinquent Loans | Commercial Portfolio | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	209	281
Domestic credit card: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	134,267	127,066
Total	140,320	131,581
Domestic credit card: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Total	1,820	1,405
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	1,820	1,405
Domestic credit card: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Total	1,329	975
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	1,329	975
Domestic credit card: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Total	2,904	2,135
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	2,904	2,135
Domestic credit card: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	6,053	4,515
International card businesses: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	6,170	5,895
Total	6,463	6,149
International card businesses: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Total	105	86
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	105	86
International card businesses: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Total	67	58
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	67	58
International card businesses: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Total	121	110
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	121	110
International card businesses: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Noncurrent	$ 293	$ 254