Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021	Sep. 30, 2021
Fair Value [Line Items]
Fair value of long term debt	$ 7,700		$ 7,700		$ 8,500
Fair Value, Inputs, Level 1 [Member]
Fair Value [Line Items]
Fair value of long term debt	7,500		7,500		8,300
Fair Value, Inputs, Level 2 [Member]
Fair Value [Line Items]
Fair value of long term debt	200		200		$ 200
Deferred compensation plan assets [Member]
Fair Value [Line Items]
Unrealized gains (losses)	(3)	$ 2	0	$ 7
Exchange Traded Funds
Fair Value [Line Items]
Unrealized gains (losses)	$ (20)	$ 2	$ (6)	$ 23