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		9 Months Ended		12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net loss attributable to Class A and Class B common stockholders	$ (65,833)	$ (51,750)	$ (81,911)	$ (104,920)	$ (115,449)	$ (80,502)	$ (55,998)	$ (21,591)	$ (186,831)	$ (77,589)	$ (238,581)	$ (158,091)	$ (304,414)	$ (273,540)	$ (276,362)
Less: deemed dividend to noncontrolling interest	(2,454)	0	0	0	0	0	0	0					(2,454)	0	0
Net loss available to Class A and Class B common stockholders	$ (68,287)	$ (51,750)	$ (81,911)	$ (104,920)	$ (115,449)	$ (80,502)	$ (55,998)	$ (21,591)					$ (306,868)	$ (273,540)	$ (276,362)
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)	118,588	116,330	113,624	111,842	109,416	81,321	10,536	10,404					115,118	53,268	10,248
Net loss per share attributable to Class A and Class B common stockholders:
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.58)	$ (0.44)	$ (0.72)	$ (0.94)	$ (1.06)	$ (0.99)	$ (5.31)	$ (2.08)					$ (2.67)	$ (5.14)	$ (26.97)