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	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Net Loss Per Share
Net loss	$ (26,838)	$ (23,190)
Weighted average common shares outstanding - basic and diluted (in shares)	25,960	24,581
Net loss per share - basic and diluted (in dollars per share)	$ (1.03)	$ (0.94)