Net Loss Per Share - Basic and Diluted (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss	$ (4,247)	$ (10,471)	$ (17,759)	$ (12,775)	$ (9,040)	$ (10,779)	$ (32,477)	$ (32,594)
Denominator:
Weighted averave common shares used for basic and diluted earnings per share (in shares)	23,611,925			20,620,828			23,184,322	20,478,603
Loss per share:
Basic and diluted (in dollars per share)	$ (0.18)			$ (0.62)			$ (1.40)	$ (1.59)