Net Loss per Share Attributable to Common Stockholders - Schedule 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 available to Class A and Class B common stockholders	$ (52,370)	$ (11,954)	$ (131,122)	$ (130,415)
Denominator:
Weighted average shares used to compute net loss per share available to Class A and Class B common stockholders, basic (in shares)	174,269	138,964	172,601	129,571
Weighted average shares used to compute net loss per share available to Class A and Class B common stockholders, diluted (in shares)	174,269	138,964	172,601	129,571
Net loss per share attributable to Class A and Class B common stockholders, basic (in dollars per share)	$ (0.30)	$ (0.09)	$ (0.76)	$ (1.01)
Net loss per share attributable to Class A and Class B common stockholders, diluted (in dollars per share)	$ (0.30)	$ (0.09)	$ (0.76)	$ (1.01)