Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator:
Net (loss) income	$ (107,415)	$ 1,387	$ (117,259)	$ (55,759)
Accretion of redeemable convertible preferred stock	(2,264,838)	(269,358)	(2,646,662)	(371,522)
Net loss attributable to common stockholders - basic	(2,372,253)	(267,971)	(2,763,921)	(427,281)
Net loss attributable to common stockholders - diluted	$ (2,372,253)	$ (267,971)	$ (2,763,921)	$ (427,281)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders - basic (in shares)	95,930	76,880	83,860	76,846
Weighted-average shares used in computing net loss per share attributable to common stockholders - diluted (in shares)	95,930	76,880	83,860	76,846
Net loss per share attributable to Class A and Class B common stockholders - basic and diluted
Basic (in dollars per share)	$ (24.72)	$ (3.49)	$ (32.96)	$ (5.56)
Diluted (in dollars per share)	$ (24.72)	$ (3.49)	$ (32.96)	$ (5.56)
Common Stock
Numerator:
Net loss attributable to common stockholders - basic	$ (2,372,253)	$ (267,971)	$ (2,763,921)	$ (427,281)
Net loss attributable to common stockholders - diluted	$ (2,372,253)	$ (267,971)	$ (2,763,921)	$ (427,281)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders - basic (in shares)	95,930	76,880	83,860	76,846
Weighted-average shares used in computing net loss per share attributable to common stockholders - diluted (in shares)	95,930	76,880	83,860	76,846
Net loss per share attributable to Class A and Class B common stockholders - basic and diluted
Basic (in dollars per share)	$ (24.72)	$ (3.49)	$ (32.96)	$ (5.56)
Diluted (in dollars per share)	$ (24.72)	$ (3.49)	$ (32.96)	$ (5.56)