Loans - Loan Portfolio Composition and Aging Analysis (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Current	$ 303,586	$ 307,695
Total	$ 315,154	$ 320,472
Current, percentage of total loans	96.33%	96.01%
Percentage of total loans	100.00%	100.00%
Unamortized premiums and discounts, deferred fees and costs	$ 1,300	$ 1,400
Credit Card:
Financing Receivable, Past Due [Line Items]
Current	143,817	147,412
Total	150,594	154,547
Consumer Banking:
Financing Receivable, Past Due [Line Items]
Current	70,700	70,097
Total	75,099	75,437
Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Current	69,431	68,768
Total	73,801	74,075
Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Current	1,269	1,329
Total	1,298	1,362
Commercial Banking:
Financing Receivable, Past Due [Line Items]
Current	89,069	90,186
Total	89,461	90,488
Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Current	34,050	34,325
Total	34,272	34,446
Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Current	55,019	55,861
Total	55,189	56,042
30-59 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 4,631	$ 5,367
Delinquent Loans, percentage of total loans	1.47%	1.68%
30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 1,848	$ 2,084
30-59 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	2,780	3,283
30-59 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	2,769	3,268
30-59 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	11	15
Total	11	15
30-59 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	3	0
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	3	0
60-89 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 2,816	$ 3,119
Delinquent Loans, percentage of total loans	0.89%	0.97%
60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 1,446	$ 1,547
60-89 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,247	1,558
60-89 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,244	1,555
60-89 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	3	3
Total	3	3
60-89 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	123	14
60-89 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	94	14
60-89 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	29	0
Greater than 90 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 4,121	$ 4,291
Delinquent Loans, percentage of total loans	1.31%	1.34%
Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 3,483	$ 3,504
Greater than 90 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	372	499
Greater than 90 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	357	484
Greater than 90 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	15	15
Total	15	15
Greater than 90 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	266	288
Greater than 90 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	128	107
Greater than 90 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	138	181
Total Delinquent Loans
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 11,568	$ 12,777
Total Delinquent Loans, percentage of total loans	3.67%	3.99%
Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 6,777	$ 7,135
Total Delinquent Loans | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	4,399	5,340
Total Delinquent Loans | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	4,370	5,307
Total Delinquent Loans | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	29	33
Total Delinquent Loans | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	392	302
Total Delinquent Loans | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	222	121
Total Delinquent Loans | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	170	181
Domestic credit card: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	137,416	140,860
Total	143,861	147,666
Domestic credit card: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,735	1,968
Total	1,735	1,968
Domestic credit card: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,371	1,471
Total	1,371	1,471
Domestic credit card: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	3,339	3,367
Total	3,339	3,367
Domestic credit card: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	6,445	6,806
International card businesses: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	6,401	6,552
Total	6,733	6,881
International card businesses: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	113	116
Total	113	116
International card businesses: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	75	76
Total	75	76
International card businesses: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	144	137
Total	144	137
International card businesses: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 332	$ 329