Net Loss Per Share Attributable to Common Stockholders - Calculation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (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 common stockholders	$ (100,748)	$ (1,159,501)	$ (241,944)	$ (1,200,921)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	586,737	443,340	581,518	285,955
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.17)	$ (2.62)	$ (0.42)	$ (4.20)
Class A
Numerator:
Net loss attributable to common stockholders	$ (70,961)	$ (189,368)	$ (165,255)	$ (151,947)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	413,262	72,406	397,194	36,180
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.17)	$ (2.62)	$ (0.42)	$ (4.20)
Class B
Numerator:
Net loss attributable to common stockholders	$ (29,787)	$ (970,133)	$ (76,689)	$ (1,048,974)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	173,475	370,934	184,324	249,775
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.17)	$ (2.62)	$ (0.42)	$ (4.20)