Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year		$ 7,755	$ 4,779	$ 6,121
Charged to Costs & Expenses		9,761	5,411	(248)
Other Changes Add (Deduct)	[1]	(9,141)	(2,435)	(1,094)
Balance at End of Year		$ 8,375	$ 7,755	$ 4,779

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