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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net loss	$ (49,788)	$ (27,335)	$ (116,107)	$ (73,684)
Weighted-average shares used to compute basic and diluted net loss per share	35,680	29,574	35,336	29,495
Basic and diluted net loss per common share	$ (1.40)	$ (0.92)	$ (3.29)	$ (2.50)