Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year		$ 6,121	$ 8,378	$ 8,002
Charged to Costs & Expenses		(248)	3,441	9,541
Other Changes Add (Deduct)	[1]	(1,094)	(5,698)	(9,165)
Balance at End of Year		$ 4,779	$ 6,121	$ 8,378

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