Net Loss Per Share - Schedule of Anti-dilutive Weighted-Average Equity Instruments Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share Basic [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	4,178,454	3,285,851
Awards under Equity Incentive Plan [Member]
Earnings Per Share Basic [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	3,133,827	1,786,438
Nonvested Restricted Shares and Restricted Stock Units [Member]
Earnings Per Share Basic [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	143,125	207,768
Warrants to Purchase Common Stock [Member]
Earnings Per Share Basic [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	901,502	1,291,645