Valuation and Qualifying Accounts (Detail) - Allowance for Doubtful Accounts - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year		$ 4,419	$ 6,713	$ 9,220
Charged to Costs & Expenses		1,639	(639)	3,738
Other Changes Add (Deduct)	[1]	(518)	(1,655)	(6,245)
Balance at End of Year		$ 5,540	$ 4,419	$ 6,713

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