Net Loss Per Share - Summary of Basic and Diluted Net Loss Per Share (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
Numerator:
Net loss	$ (34,747)	$ (25,027)	$ (65,290)	$ (41,898)
Denominator:
Weighted average common stock outstanding-basic	32,062,298	27,860,332	31,835,194	26,765,705
Dilutive effect of shares of common stock equivalents resulting from common stock options	0	0	0	0
Weighted average common stock outstanding-diluted	32,062,298	27,860,332	31,835,194	26,765,705
Net loss per share-basic and diluted	$ (1.08)	$ (0.90)	$ (2.05)	$ (1.57)