Net Loss Per Share - Summary of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share Basic And Diluted [Abstract]
Net loss	$ (65,807)	$ (77,189)	$ (63,228)	$ (41,059)	$ (142,996)	$ (104,287)
Weighted-average number of shares outstanding used to compute net loss per share attributable to common stockholders, basic and diluted	136,507,177		31,599,497		136,002,344	20,035,476
Net loss per share attributable to common stockholders, basic and diluted	$ (0.48)		$ (2.00)		$ (1.05)	$ (5.21)