Net Loss Per Share - Computation of Basic and Diluted Net Income (Loss) Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net loss	$ (11,226)	$ (9,158)
Denominator (basic and diluted):
Weighted average common shares outstanding	94,748,645	94,033,035
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.12)	$ (0.10)