Loans - Loan Portfolio Composition and Aging Analysis (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Current	$ 306,641	$ 307,695
Total	$ 318,186	$ 320,472
Current, percentage of total loans	96.37%	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	147,484	147,412
Total	153,895	154,547
Consumer Banking:
Financing Receivable, Past Due [Line Items]
Current	70,858	70,097
Total	75,663	75,437
Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Current	69,615	68,768
Total	74,385	74,075
Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Current	1,243	1,329
Total	1,278	1,362
Commercial Banking:
Financing Receivable, Past Due [Line Items]
Current	88,299	90,186
Total	88,628	90,488
Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Current	32,643	34,325
Total	32,832	34,446
Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Current	55,656	55,861
Total	55,796	56,042
30-59 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 4,808	$ 5,367
Delinquent Loans, percentage of total loans	1.51%	1.68%
30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 1,884	$ 2,084
30-59 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	2,895	3,283
30-59 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	2,873	3,268
30-59 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	22	15
Total	22	15
30-59 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	29	0
30-59 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	21	0
30-59 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	8	0
60-89 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 2,890	$ 3,119
Delinquent Loans, percentage of total loans	0.91%	0.97%
60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 1,419	$ 1,547
60-89 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,466	1,558
60-89 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,462	1,555
60-89 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	4	3
Total	4	3
60-89 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	5	14
60-89 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	5	14
60-89 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	0	0
Greater than 90 days
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 3,847	$ 4,291
Delinquent Loans, percentage of total loans	1.21%	1.34%
Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 3,108	$ 3,504
Greater than 90 days | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	444	499
Greater than 90 days | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	435	484
Greater than 90 days | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	9	15
Total	9	15
Greater than 90 days | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	295	288
Greater than 90 days | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	163	107
Greater than 90 days | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	132	181
Total Delinquent Loans
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 11,545	$ 12,777
Total Delinquent Loans, percentage of total loans	3.63%	3.99%
Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 6,411	$ 7,135
Total Delinquent Loans | Consumer Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	4,805	5,340
Total Delinquent Loans | Consumer Banking: | Auto
Financing Receivable, Past Due [Line Items]
Delinquent Loans	4,770	5,307
Total Delinquent Loans | Consumer Banking: | Retail banking
Financing Receivable, Past Due [Line Items]
Delinquent Loans	35	33
Total Delinquent Loans | Commercial Banking:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	329	302
Total Delinquent Loans | Commercial Banking: | Commercial and multifamily real estate
Financing Receivable, Past Due [Line Items]
Delinquent Loans	189	121
Total Delinquent Loans | Commercial Banking: | Commercial and industrial
Financing Receivable, Past Due [Line Items]
Delinquent Loans	140	181
Domestic credit card: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	140,978	140,860
Total	147,065	147,666
Domestic credit card: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,770	1,968
Total	1,770	1,968
Domestic credit card: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	1,350	1,471
Total	1,350	1,471
Domestic credit card: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	2,967	3,367
Total	2,967	3,367
Domestic credit card: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	6,087	6,806
International card businesses: | Credit Card:
Financing Receivable, Past Due [Line Items]
Current	6,506	6,552
Total	6,830	6,881
International card businesses: | 30-59 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	114	116
Total	114	116
International card businesses: | 60-89 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	69	76
Total	69	76
International card businesses: | Greater than 90 days | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	141	137
Total	141	137
International card businesses: | Total Delinquent Loans | Credit Card:
Financing Receivable, Past Due [Line Items]
Delinquent Loans	$ 324	$ 329