Net Loss per Share - Summary of Securities Not Included in Diluted Per Share Calculations (Detail) - shares	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities not included in the diluted per share calculations, amount	7,202,660	6,029,517
Option to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities not included in the diluted per share calculations, amount	5,865,766	4,692,623
Warrants to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities not included in the diluted per share calculations, amount	1,336,894	1,336,894