Stockholders' Equity - Stock Option Activity (Detail) - $ / shares	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Beginning balance	2,334,326	2,824,964	3,512,286
Number of Shares, Granted	1,927,500	0	651,563
Number of Shares, Exercised	(232,203)	(108,135)	(1,103,582)
Number of Shares, Cancelled	(381,918)	(382,503)	(235,303)
Number of Shares, Ending balance	3,647,705	2,334,326	2,824,964	3,512,286
Weighted Average Exercise Price Per Share, Beginning balance	$ 4.11	$ 4.09	$ 3.39
Weighted Average Exercise Price Per Share, Granted	2.92		3.63
Weighted Average Exercise Price Per Share, Exercised	1.06	1.27	0.90
Weighted Average Exercise Price Per Share, Cancelled	3.85	4.77	7.26
Weighted Average Exercise Price Per Share, Ending balance	$ 3.70	$ 4.11	$ 4.09	$ 3.39
Weighted Average Remaining Contractual Term (in Years)	7 years 1 month 24 days	5 years 5 months 16 days	7 years 3 months 15 days	6 years 5 months 16 days