CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Net revenues	$ 21,846	$ 22,977	$ 20,609
Operating Expenses
Personnel	3,785	3,444	3,170
Marketing	971	1,105	988
Network and processing	727	721	686
Professional fees	408	454	446
Depreciation and amortization	767	656	613
General and administrative	1,096	1,196	1,145
Litigation provision	11	400	607
Total operating expenses	7,765	7,976	7,655
Operating income	14,081	15,001	12,954
Non-operating Income (Expense)
Interest expense, net	(516)	(533)	(612)
Investment income and other	225	416	464
Total non-operating income (expense)	(291)	(117)	(148)
Income before income taxes	13,790	14,884	12,806
Income tax provision	2,924	2,804	2,505
Net income	$ 10,866	$ 12,080	$ 10,301
Class A common stock
Earnings Per Share [Abstract]
Basic earnings per share (in dollars per share)	$ 4.90	$ 5.32	$ 4.43
Basic weighted-average shares outstanding (in shares)	1,697	1,742	1,792
Diluted earnings per share (in dollars per share)	$ 4.89	$ 5.32	$ 4.42
Diluted weighted-average shares outstanding (in shares)	2,223	2,272	2,329
Class B common stock
Earnings Per Share [Abstract]
Basic earnings per share (in dollars per share)	$ 7.94	$ 8.68	$ 7.28
Basic weighted-average shares outstanding (in shares)	245	245	245
Diluted earnings per share (in dollars per share)	$ 7.93	$ 8.66	$ 7.27
Diluted weighted-average shares outstanding (in shares)	245	245	245
Class C common stock
Earnings Per Share [Abstract]
Basic earnings per share (in dollars per share)	$ 19.58	$ 21.30	$ 17.72
Basic weighted-average shares outstanding (in shares)	11	12	12
Diluted earnings per share (in dollars per share)	$ 19.56	$ 21.26	$ 17.69
Diluted weighted-average shares outstanding (in shares)	11	12	12