Net Loss per Share - Summary of Securities Not Included in Diluted Per Share Calculations (Detail) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities not included in the diluted per share calculations, amount	3,351,881	360,133
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	525,194	293,288
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	2,826,687	66,845