Stock-based Compensation Plans - Schedule of Stock Option Activity (Detail) - $ / shares	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Share-Based Payment Arrangement [Abstract]
Number of Options Outstanding, Beginning balance	1,161,000	922,000	940,000
Number of Options, Granted	311,000	342,000	274,000
Number of Options, Exercised	(20,000)	(45,000)	(248,000)
Number of Options, Forfeited and expired	(90,000)	(58,000)	(44,000)
Number of Options Outstanding, Ending balance	1,362,000	1,161,000	922,000
Number of Options, vested and exercisable	724,000
Weighted Average Exercise Price, Beginning Balance	$ 40.66	$ 39.39	$ 35.18
Weighted Average Exercise Price, Granted	34.73	42.10	40.95
Weighted Average Exercise Price, Exercised	21.50	21.24	24.22
Weighted Average Exercise Price, Forfeited and expired	41.77	43.99	44.58
Weighted Average Exercise Price, Ending balance	39.52	$ 40.66	$ 39.39
Weighted Average Exercise Price, vested and exercisable	$ 40.47