Revenues - Schedule of Net Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Net revenues	$ 8,634	$ 7,936
U.S.
Disaggregation of Revenue [Line Items]
Net revenues	3,645	3,567
International
Disaggregation of Revenue [Line Items]
Net revenues	4,989	4,369
Service revenues
Disaggregation of Revenue [Line Items]
Net revenues	3,915	3,511
Data processing revenues
Disaggregation of Revenue [Line Items]
Net revenues	4,356	3,827
International transaction revenues
Disaggregation of Revenue [Line Items]
Net revenues	3,019	2,797
Other revenues
Disaggregation of Revenue [Line Items]
Net revenues	692	587
Client incentives
Disaggregation of Revenue [Line Items]
Net revenues	$ (3,348)	$ (2,786)