Stockholders' Equity - Schedule of As-Converted Class B Common Stock (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Stockholders' Equity Note [Abstract]
Reduction in equivalent number of as-converted shares of class A common stock (in shares)	1
Effective price per share (in dollars per share)	$ 217.61
Deposits under the U.S. retrospective responsibility plan	$ 250	$ 0