Net Loss per Share - Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net loss	$ (22,867)	$ (16,659)	$ (19,907)
Denominator:
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares)	118,698,567	109,814,604	52,327,518
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.19)	$ (0.15)	$ (0.38)