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				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net loss	$ (3,044)	$ (4,704)	$ (9,848)	$ (8,981)	$ (7,748)	$ (18,829)
Basic and diluted net loss per common share	$ (0.27)		$ (1.64)		$ (0.69)	$ (3.14)
Weighted-average common shares used to compute basic and diluted net loss per share	11,280		6,023		11,277	6,002