Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year		$ 5,540	$ 4,419	$ 6,713
Charged to Costs & Expenses		6,283	1,639	(639)
Other Changes Add (Deduct)	[1]	(3,821)	(518)	(1,655)
Balance at End of Year		$ 8,002	$ 5,540	$ 4,419

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