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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net loss	$ (9,848)	$ (36,597)	$ (18,829)	$ (66,319)
Weighted-average shares used to compute basic and diluted net loss per share	36,134	35,316	36,010	35,001
Basic and diluted net loss per common share	$ (0.27)	$ (1.04)	$ (0.52)	$ (1.89)