Net Loss Per Common Share - Computation of Basic and Diluted Net Loss per Share Attributable to Common Stock holders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss	$ (4,677)	$ (18,293)	$ (34,179)	$ (37,268)
Denominator:
Weighted-average shares used to compute net loss per common share, basic and diluted (in shares)	28,050,210	25,247,831	27,358,096	24,818,482
Net loss per common share, basic and diluted (in USD per share)	$ (0.17)	$ (0.72)	$ (1.25)	$ (1.50)