Service Fees and Other Revenue and Other Expenses - Other Expenses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Service Fees and Other Revenue and Other Expenses [Abstract]
Data processing and equipment	$ 858	$ 751	$ 2,442	$ 2,176
Professional services	675	623	1,842	1,755
Gain on sale of GBTG equity method investment	(982)	0	(982)	0
Other	764	406	1,206	1,181
Total Other expenses	1,315	$ 1,780	$ 4,508	$ 5,112
Loss contingency accrual, loss (reversal of loss)	$ 400