Service Fees and Other Revenue and Other Expenses - Other Expenses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Service Fees and Other Revenue and Other Expenses [Abstract]
Data processing and equipment	$ 2,805	$ 2,606	$ 2,431
Professional services	2,029	2,074	1,958
Net unrealized and realized losses (gains) on Amex Ventures investments	152	302	(767)
Other	1,821	1,499	1,195
Total Other expenses	$ 6,807	$ 6,481	$ 4,817