Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Net loss	$ (12,559)	$ (13,039)
Denominator:
Weighted average shares of common stock outstanding (in shares)	26,080,806	20,171,518
Weighted average shares of common stock outstanding	26,080,806	20,171,518
Net loss per share, basic and diluted (in dollars per share)	$ (0.48)	$ (0.65)