Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Jan. 31, 2021	Jan. 26, 2021	Jan. 31, 2020
Stockholders Equity Note [Line Items]
Share repurchase program					$ 9,500
January 2020 share repurchase program remaining authorized funds	$ 3,700
Cash dividends declared and paid, at a quarterly amount per Class A share	$ 703	$ 671
Subsequent Event
Stockholders Equity Note [Line Items]
Share repurchase program			$ 8,000
Subsequent Event | Class A common stock
Stockholders Equity Note [Line Items]
Quarterly cash dividend (in dollars per share)				$ 0.32