Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year		$ 6,434	$ 8,375	$ 7,755
Charged to Costs & Expenses		6,879	8,042	9,761
Other Changes Add (Deduct)	[1]	(6,117)	(9,983)	(9,141)
Balance at End of Year		$ 7,196	$ 6,434	$ 8,375

[1] Bad debts written off (net of recoveries).