Net Income (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				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Net Loss Per Share
Net income (loss)	$ 803	$ (10,676)	$ (6,762)	$ (10,286)	$ (9,873)	$ (17,048)
Weighted average common shares outstanding - basic	26,722		25,907		26,572	25,755
Net income (loss) per share-basic (in dollars per share)	$ 0.03		$ (0.26)		$ (0.37)	$ (0.66)
Weighted average common shares outstanding - diluted	26,722		25,907		26,572	25,755
Net income (loss) per share-diluted (in dollars per share)	$ 0.03		$ (0.26)		$ (0.37)	$ (0.66)