Net Loss per Share of Common Stock - Summary of Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share [Abstract]
Net loss	$ (4,704)	$ (8,981)
Basic and diluted net loss per common share	$ (0.42)	$ (1.50)
Weighted-average common shares used to compute basic and diluted net loss per share	11,273	6,003