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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net loss attributable to common stockholders - basic and diluted	$ (20,379)	$ (13,834)	$ (62,052)	$ (67,419)
Weighted-average shares outstanding	29,354	24,195	28,825	17,138
Weighted-average shares used to compute basic and diluted net loss per share	29,354	24,195	28,825	17,138
Basic and diluted net loss per common share	$ (0.69)	$ (0.57)	$ (2.15)	$ (3.93)