CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue		$ 375,610	$ 307,421	$ 254,324
Cost of revenue	[1],[2]	83,917	76,524	77,982
Gross profit		291,693	230,897	176,342
Operating expenses:
Research and development	[2]	112,989	90,545	106,188
Sales and marketing	[1],[2]	172,376	123,573	95,783
General and administrative	[2]	87,909	83,288	97,339
Restructuring		0	(66)	3,525
Total operating expenses		373,274	297,340	302,835
Loss from operations		(81,581)	(66,443)	(126,493)
Interest expense		10,257	14,157	27,801
Other non-operating (income) expense, net		(1,436)	(3,962)	298
Loss before income taxes		(90,402)	(76,638)	(154,592)
Provision for (benefit from) income taxes		1,179	(2,779)	148
Net loss		$ (91,581)	$ (73,859)	$ (154,740)
Net loss per share, basic and diluted		$ (0.65)	$ (0.56)	$ (1.43)
Weighted-average shares used in computing basic and diluted net loss per share		139,887	131,568	107,900

[1] ^{Includes amortization of acquisition intangible assets as follows:}

[2] ^{Includes stock-based compensation, net of amounts capitalized as follows:}