Stock Options and Employee Stock Purchase Plan - Summary of Options Activity (Detail) - $ / shares	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Options, Outstanding Beginning Balance (in shares)	1,449,409	1,240,941
Options, Granted (in shares)	243,881	317,619
Options, Exercised (in shares)	(2,968)	(11,117)
Options, Forfeited (in shares)	(87,500)	(98,034)
Options, Outstanding Ending Balance (in shares)	1,602,822	1,449,409
Options, Exercisable Ending Balance (in shares)	1,062,837	885,777
Weighted Average Exercise Price, Outstanding Beginning Balance (usd per share)	$ 10.03	$ 10.31
Weighted Average Exercise Price, Granted (usd per share)	7.16	9.22
Weighted Average Exercise Price, Exercised (usd per share)	6.74	7.27
Weighted Average Exercise Price, Forfeited (usd per share)	11.02	11.27
Weighted Average Exercise Price, Outstanding Ending Balance (usd per share)	9.51	10.03
Weighted-Average Grant Date Fair Value, Granted (usd per share)	$ 2.62	$ 3.18