Loans - Credit Card Delinquency Status (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	$ 320,472	$ 312,331
Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	154,091	137,394
Revolving Loans Converted to Term	456	336
Total	154,547	137,730
Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	147,254	131,284
Revolving Loans Converted to Term	412	297
Total	147,666	131,581
International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	6,837	6,110
Revolving Loans Converted to Term	44	39
Total	6,881	6,149
Current | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	140,521	126,811
Revolving Loans Converted to Term	339	255
Total	140,860	127,066
Current | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	6,521	5,866
Revolving Loans Converted to Term	31	29
Total	6,552	5,895
30-59 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	1,940	1,388
Revolving Loans Converted to Term	28	17
Total	1,968	1,405
30-59 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	112	83
Revolving Loans Converted to Term	4	3
Total	116	86
60-89 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	1,454	964
Revolving Loans Converted to Term	17	11
Total	1,471	975
60-89 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	72	55
Revolving Loans Converted to Term	4	3
Total	76	58
Greater than 90 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	3,339	2,121
Revolving Loans Converted to Term	28	14
Total	3,367	2,135
Greater than 90 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	132	106
Revolving Loans Converted to Term	5	4
Total	$ 137	$ 110