Stockholders' Equity - Stock Option Activity (Detail) - $ / shares	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding, September 30, 2016	3,015,374
Number of Shares, Granted	101,800
Number of Shares, Exercised	(5,760)
Number of Shares, Cancelled	(4,333)
Number of Shares, Outstanding, December 31, 2016	3,107,081	3,015,374
Weighted-Average Exercise Price, Outstanding, September 30, 2016	$ 3.95
Weighted-Average Exercise Price, Granted	6.10
Weighted-Average Exercise Price, Exercised	3.02
Weighted-Average Exercise Price, Cancelled	2.82
Weighted-Average Exercise Price, Outstanding, December 31, 2016	$ 4.02	$ 3.95
Weighted-Average Remaining Contractual Term (in Years), Outstanding	6 years 3 months 18 days	6 years 4 months 24 days