Loans - Credit Card Delinquency Status (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	$ 315,154	$ 320,472
Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	150,103	154,091
Revolving Loans Converted to Term	491	456
Total	150,594	154,547
Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	143,417	147,254
Revolving Loans Converted to Term	444	412
Total	143,861	147,666
International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	6,686	6,837
Revolving Loans Converted to Term	47	44
Total	6,733	6,881
Current | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	137,043	140,521
Revolving Loans Converted to Term	373	339
Total	137,416	140,860
Current | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	6,368	6,521
Revolving Loans Converted to Term	33	31
Total	6,401	6,552
30-59 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	1,709	1,940
Revolving Loans Converted to Term	26	28
Total	1,735	1,968
30-59 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	108	112
Revolving Loans Converted to Term	5	4
Total	113	116
60-89 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	1,352	1,454
Revolving Loans Converted to Term	19	17
Total	1,371	1,471
60-89 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	71	72
Revolving Loans Converted to Term	4	4
Total	75	76
Greater than 90 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	3,313	3,339
Revolving Loans Converted to Term	26	28
Total	3,339	3,367
Greater than 90 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	139	132
Revolving Loans Converted to Term	5	5
Total	$ 144	$ 137