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
	Mar. 31, 2020	Mar. 31, 2019
Numerator:
Net loss attributable to common stockholders	$ (141,196)	$ (41,420)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	576,302	127,346
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.25)	$ (0.33)
Class A
Numerator:
Net loss attributable to common stockholders	$ (93,363)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	381,068
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.25)
Class B
Numerator:
Net loss attributable to common stockholders	$ (47,833)
Denominator:
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	195,234
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.25)