Receivables - Activity of Allowance for Doubtful Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of year	$ 2,927	$ 3,157
Add: expense	0	1,485	$ 327
Less: write-offs (net of recoveries)	(801)	(1,715)
Balance, end of year	$ 2,126	$ 2,927	$ 3,157