Net Loss per Share - Computation of Basic and Diluted Net Loss per Share of Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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	$ (26,254)	$ (21,482)	$ (53,425)	$ (40,650)
Weighted-average shares used to compute basic and diluted net loss per share	92,174	86,390	91,351	81,390
Net loss per share:
Basic and diluted (usd per share)	$ (0.28)	$ (0.25)	$ (0.58)	$ (0.50)