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	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net Loss Per Share
Net loss	$ (10,676)	$ (10,286)
Weighted average common shares outstanding - basic and diluted (in shares)	26,424	25,601
Net loss per share - basic and diluted (in dollars per share)	$ (0.40)	$ (0.40)