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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net loss attributable to Class A and Class B common stockholders	$ (11,954)	$ (51,750)	$ (130,415)	$ (238,581)
Denominator:
Weighted average shares used to compute net loss per share attributable to Class A and Class B common stockholders, basic and diluted (in shares)	138,964	116,330	129,571	113,948
Net loss per share attributable to Class A and Class B common stockholders, basic and diluted (in dollars per share)	$ (0.09)	$ (0.44)	$ (1.01)	$ (2.09)