Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jul. 20, 2020	Jan. 31, 2020	Jan. 31, 2019
Stockholders Equity Note [Line Items]
Share repurchase program						$ 9,500	$ 8,500
January 2020 share repurchase program remaining authorized funds	$ 7,000		$ 7,000
Cash dividends declared and paid, at a quarterly amount per Class A share	$ 663	$ 565	$ 2,002	$ 1,706
Subsequent Event | Class A common stock
Stockholders Equity Note [Line Items]
Quarterly cash dividend (in dollars per share)					$ 0.30