Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021
Accounts receivable, allowances	$ 20	$ 20
Accumulated depreciation	$ 435	$ 419
Class A Common Stock
Par value (in dollars per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	1,000,000,000	1,000,000,000
Shares issued (in shares)	127,236,783	122,414,827
Shares outstanding (in shares)	127,236,783	122,414,827
Class B Common Stock
Par value (in dollars per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	1,000,000,000	1,000,000,000
Shares issued (in shares)	387,300,086	391,970,996
Shares outstanding (in shares)	387,300,086	391,970,996