Net Loss Per Share - Computation of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Numerator:
Net income (loss) attributable to common stockholders	$ 7,540	$ (17,231)	$ (10,455)	$ (28,952)
Less: Net income allocated to participating securities	$ (7,540)
Net income (loss) available to common stockholders		$ (17,231)	$ (10,455)	$ (28,952)
Denominator:
Weighted average shares used to compute net loss per share available to common stockholders, basic and diluted	26,215	23,827	25,322	21,437
Basic and diluted		$ (0.72)	$ (0.41)	$ (1.35)