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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Net loss used to compute net loss per common share:
Basic	$ (7,380)	$ (6,016)	$ (14,897)	$ (9,279)
Adjustment for change in fair value of liability classified stock options	(30)	(58)	(162)	(100)
Diluted	$ (7,410)	$ (6,074)	$ (15,059)	$ (9,379)
Weighted average number of common shares:
Basic	17,997,194	14,408,108	17,971,702	14,401,054
Adjustment for dilutive effect of stock options	18,554	26,494	23,407	27,106
Diluted	18,015,748	14,434,602	17,995,109	14,428,160
Net loss per common share - basic	$ (0.41)	$ (0.42)	$ (0.83)	$ (0.64)
Net loss per common share - diluted	$ (0.41)	$ (0.42)	$ (0.84)	$ (0.65)