Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Loss per Share
Net loss	$ (5,828)	$ 1,998	$ (11,246)	$ (137)	$ (11,816)	$ (5,171)	$ (5,711)	$ (1,709)	$ (15,213)	$ (24,407)	$ (31,790)
Weighted average common shares outstanding:
Basic									23,179,257	22,912,217	22,779,377
Diluted									23,179,257	22,912,217	22,779,377
Basic loss per share of common stock	$ (0.25)	$ 0.09	$ (0.49)	$ (0.01)	$ (0.51)	$ (0.23)	$ (0.25)	$ (0.07)	$ (0.66)	$ (1.07)	$ (1.40)
Diluted loss per share of common stock	$ (0.25)	$ 0.09	$ (0.49)	$ (0.01)	$ (0.51)	$ (0.23)	$ (0.25)	$ (0.07)	$ (0.66)	$ (1.07)	$ (1.40)