Activity of Allowance for Doubtful Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of year	$ 3,157	$ 3,406
Add: expense	1,485	327	(122)
Less: write-offs (net of recoveries)	(1,715)	(576)
Balance, end of year	$ 2,927	$ 3,157	$ 3,406