Net Loss Per Share - Computation of Company's Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net loss attributable to common stockholders, basic	$ (110,048)	$ (107,908)	$ (120,199)
Net loss attributable to common stockholders, diluted	$ (110,048)	$ (107,908)	$ (120,199)
Weighted-average common shares used in computing net loss per share, basic (in shares)	164,521,064	147,895,561	102,001,954
Weighted-average common shares used in computing net loss per share, diluted (in shares)	164,521,064	147,895,561	102,001,954
Net loss per share, basic (USD per share)	$ (0.67)	$ (0.73)	$ (1.18)
Net loss per share, diluted (USD per share)	$ (0.67)	$ (0.73)	$ (1.18)