Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net loss attributable to common stock holders	$ (12,733)	$ (11,149)	$ (10,906)	$ (10,593)	$ (10,544)	$ (13,001)	$ (34,788)	$ (34,138)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stock - basic and diluted	1,232,921			1,197,919			1,218,815	1,194,562
Net loss per share attributable to common stockholders - basic and diluted	$ (10.33)			$ (8.84)			$ (28.54)	$ (28.58)