Net Loss Per Share - Summary of Basic and Diluted Net Loss Per Share of Common Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Net loss	$ (10,545)	$ (15,580)
Weighted-average common shares outstanding, basic and diluted	42,016,831	40,547,669
Net loss per share, basic and diluted (in dollars per share)	$ (0.25)	$ (0.38)