Loans - Credit Card Delinquency Status (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	$ 318,186	$ 320,472
Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	153,373	154,091
Revolving Loans Converted to Term	522	456
Total	153,895	154,547
Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	146,592	147,254
Revolving Loans Converted to Term	473	412
Total	147,065	147,666
International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	6,781	6,837
Revolving Loans Converted to Term	49	44
Total	6,830	6,881
Current | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	140,576	140,521
Revolving Loans Converted to Term	402	339
Total	140,978	140,860
Current | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	6,470	6,521
Revolving Loans Converted to Term	36	31
Total	6,506	6,552
30-59 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	1,743	1,940
Revolving Loans Converted to Term	27	28
Total	1,770	1,968
30-59 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	109	112
Revolving Loans Converted to Term	5	4
Total	114	116
60-89 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	1,333	1,454
Revolving Loans Converted to Term	17	17
Total	1,350	1,471
60-89 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	66	72
Revolving Loans Converted to Term	3	4
Total	69	76
Greater than 90 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	2,940	3,339
Revolving Loans Converted to Term	27	28
Total	2,967	3,367
Greater than 90 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	136	132
Revolving Loans Converted to Term	5	5
Total	$ 141	$ 137