Net Loss Per Share - Summary of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net loss	$ (37,796)	$ (24,035)	$ (103,086)	$ (65,933)
Denominator:
Weighted average common stock outstanding—basic	32,975,897	28,737,743	32,218,204	27,430,275
Dilutive effect of shares of common stock equivalents resulting from common stock options	0	0	0	0
Weighted average common stock outstanding—diluted	32,975,897	28,737,743	32,218,204	27,430,275
Net loss per share—basic and diluted	$ (1.15)	$ (0.84)	$ (3.20)	$ (2.40)