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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net loss attributable to Class A and Class B common stockholders	$ (42,512)	$ (81,911)	$ (118,461)	$ (186,831)
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)	125,928	113,622	124,823	112,737
Net loss per share attributable to Class A and Class B common stockholders, basic and diluted (in dollars per share)	$ (0.34)	$ (0.72)	$ (0.95)	$ (1.66)