CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Net revenues	$ 22,977	$ 20,609	$ 18,358
Operating Expenses
Personnel	3,444	3,170	2,628
Marketing	1,105	988	922
Network and processing	721	686	620
Professional fees	454	446	409
Depreciation and amortization	656	613	556
General and administrative	1,196	1,145	1,060
Litigation provision (Note 20)	400	607	19
Total operating expenses	7,976	7,655	6,214
Operating income	15,001	12,954	12,144
Non-operating Income (Expense)
Interest expense, net	(533)	(612)	(563)
Investment income and other	416	464	113
Total non-operating income (expense)	(117)	(148)	(450)
Income before income taxes	14,884	12,806	11,694
Income tax provision (Note 19)	2,804	2,505	4,995
Net income	$ 12,080	$ 10,301	$ 6,699
Class A common stock
Earnings Per Share [Abstract]
Basic earnings per share (Note 15) (in dollars per share)	$ 5.32	$ 4.43	$ 2.80
Basic weighted-average shares outstanding (Note 15) (in shares)	1,742	1,792	1,845
Diluted earnings per share (Note 15) (in dollars per share)	$ 5.32	$ 4.42	$ 2.80
Diluted weighted-average shares outstanding (Note 15) (in shares)	2,272	2,329	2,395
Class B common stock
Earnings Per Share [Abstract]
Basic earnings per share (Note 15) (in dollars per share)	$ 8.68	$ 7.28	$ 4.62
Basic weighted-average shares outstanding (Note 15) (in shares)	245	245	245
Diluted earnings per share (Note 15) (in dollars per share)	$ 8.66	$ 7.27	$ 4.61
Diluted weighted-average shares outstanding (Note 15) (in shares)	245	245	245
Class C common stock
Earnings Per Share [Abstract]
Basic earnings per share (Note 15) (in dollars per share)	$ 21.30	$ 17.72	$ 11.21
Basic weighted-average shares outstanding (Note 15) (in shares)	12	12	14
Diluted earnings per share (Note 15) (in dollars per share)	$ 21.26	$ 17.69	$ 11.19
Diluted weighted-average shares outstanding (Note 15) (in shares)	12	12	14