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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Net loss	$ (13,452)	$ (9,244)	$ (29,032)	$ (16,926)
Accretion of preferred stock to redemption value		(23,788)		(35,061)
Net loss attributable to common stockholders, basic and diluted	$ (13,452)	$ (33,032)	$ (29,032)	$ (51,987)
Weighted-average common shares outstanding, basic and diluted	41,063,613	12,745,051	40,805,641	12,693,900
Net loss per share attributable to common stockholders, basic and diluted	$ (0.33)	$ (2.59)	$ (0.71)	$ (4.10)