Summary of Significant Accounting Policies - Computation of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss, basic and diluted	$ (78,994)	$ (57,002)
Denominator:
Weighted average common shares outstanding	67,200	52,520
Weighted average unvested common shares subject to repurchase	(180)	(286)
Weighted average common shares outstanding - basic and diluted	67,020	52,234
Net loss per share, basic and diluted	$ (1.18)	$ (1.09)