Net Income (Loss) Per Common Share - Reconciliation of the Numerators and Denominators of Basic and Diluted Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net loss used to compute net loss per common share:
Basic	$ (7,742)	$ (7,714)	$ (22,639)	$ (16,993)
Adjustment for change in fair value of liability classified stock options	(20)		(182)
Diluted	$ (7,762)	$ (7,714)	$ (22,821)	$ (16,993)
Weighted average number of common shares:
Basic	17,998,420	15,268,964	17,980,608	14,690,357
Adjustment for dilutive effect of stock options	11,559		19,458
Diluted	18,009,979	15,268,964	18,000,066	14,690,357
Net loss per common share - basic	$ (0.43)	$ (0.51)	$ (1.26)	$ (1.16)
Net loss per common share - diluted	$ (0.43)	$ (0.51)	$ (1.27)	$ (1.16)