Net Loss Per Share Attributable to Common Stockholders - Summary of Calculation 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	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net loss	$ (115,490)	$ (89,452)	$ (617,179)	$ (143,297)
Less: Accretion of redeemable convertible preferred stock	0	(11,943)	(4,135)	(11,943)
Net loss attributable to common stockholders, basic	(115,490)	(101,395)	(621,314)	(155,240)
Net loss attributable to common stockholders, diluted	$ (115,490)	$ (101,395)	$ (621,314)	$ (155,240)
Denominator:
Weighted-average shares used in computing net loss per share, basic (in shares)	212,802,379	58,606,231	152,469,098	57,584,574
Weighted-average shares used in computing net loss per share, diluted (in shares)	212,802,379	58,606,231	152,469,098	57,584,574
Net loss per share:
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.54)	$ (1.73)	$ (4.08)	$ (2.70)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.54)	$ (1.73)	$ (4.08)	$ (2.70)