Revenues - Schedule of Net Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Net revenues	$ 7,189	$ 5,729	$ 14,248	$ 11,416
U.S.
Disaggregation of Revenue [Line Items]
Net revenues	3,079	2,683	6,257	5,350
International
Disaggregation of Revenue [Line Items]
Net revenues	4,110	3,046	7,991	6,066
Service revenues
Disaggregation of Revenue [Line Items]
Net revenues	3,521	2,845	6,714	5,522
Data processing revenues
Disaggregation of Revenue [Line Items]
Net revenues	3,480	2,996	7,094	6,029
International transaction revenues
Disaggregation of Revenue [Line Items]
Net revenues	2,208	1,488	4,382	2,939
Other revenues
Disaggregation of Revenue [Line Items]
Net revenues	474	392	923	776
Client incentives
Disaggregation of Revenue [Line Items]
Net revenues	$ (2,494)	$ (1,992)	$ (4,865)	$ (3,850)