CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenue	$ 272,485	$ 261,249	$ 544,425	$ 463,160
Costs and expenses:
Cost of revenue	108,259	105,415	207,491	179,109
Research and development	136,593	801,879	282,297	874,323
Sales and marketing	86,483	296,919	203,510	373,313
General and administrative	45,680	224,179	101,747	248,384
Total costs and expenses	377,015	1,428,392	795,045	1,675,129
Loss from operations	(104,530)	(1,167,143)	(250,620)	(1,211,969)
Interest income	4,218	8,127	11,369	12,186
Interest expense and other income (expense), net	(16)	(448)	(2,093)	(948)
Loss before provision for income taxes	(100,328)	(1,159,464)	(241,344)	(1,200,731)
Provision for income taxes	420	37	600	190
Net loss	$ (100,748)	$ (1,159,501)	$ (241,944)	$ (1,200,921)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.17)	$ (2.62)	$ (0.42)	$ (4.20)
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