Stock-Based Compensation - Schedule of Stock Option Activity (Detail) - USD ($)	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding beginning balance		81,820
Shares, Granted	0	1,211,917	0
Shares, Exercised		(19,674)
Shares, Expired		(53,864)
Shares, Outstanding ending balance		1,220,199		81,820
Shares, Options exercisable		8,282
Shares, Options vested and expected to vest		1,018,478
Weighted- average price per share, Outstanding beginning balance		$ 4.48
Weighted- average price per share, Granted		9.73
Weighted- average price per share, Exercised		4.55
Weighted- average price per share, Expired		4.59
Weighted- average price per share, Outstanding ending balance		9.70		$ 4.48
Weighted- average price per share, Options exercisable		4.83
Weighted- average price per share, Options vested and expected to vest		$ 9.70
Weighted- average remaining contractual term, Beginning period		9 years 7 months 6 days		3 years
Weighted- average remaining contractual term, Options exercisable		2 years 4 months 24 days
Weighted- average remaining contractual term, Options vested and expected to vest		9 years 7 months 6 days
Aggregate intrinsic value, Outstanding beginning balance		$ 255,777
Aggregate intrinsic value, Outstanding ending balance				$ 255,777