Loans - Credit Card Delinquency Status (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Line Items]
Total	$ 314,780	$ 312,331
Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	146,362	137,394
Revolving Loans Converted to Term	421	336
Total	146,783	137,730
Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	139,940	131,284
Revolving Loans Converted to Term	380	297
Total	140,320	131,581
International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	6,422	6,110
Revolving Loans Converted to Term	41	39
Total	6,463	6,149
Current | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	133,953	126,811
Revolving Loans Converted to Term	314	255
Total	134,267	127,066
Current | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	6,140	5,866
Revolving Loans Converted to Term	30	29
Total	6,170	5,895
30-59 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	1,796	1,388
Revolving Loans Converted to Term	24	17
Total	1,820	1,405
30-59 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	101	83
Revolving Loans Converted to Term	4	3
Total	105	86
60-89 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	1,312	964
Revolving Loans Converted to Term	17	11
Total	1,329	975
60-89 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	64	55
Revolving Loans Converted to Term	3	3
Total	67	58
Greater than 90 days | Domestic credit card: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	2,879	2,121
Revolving Loans Converted to Term	25	14
Total	2,904	2,135
Greater than 90 days | International card businesses: | Credit Card:
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving Loans	117	106
Revolving Loans Converted to Term	4	4
Total	$ 121	$ 110