CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue		$ 307,421	$ 254,324	$ 218,773
Cost of revenue	[1],[2]	76,524	77,982	62,679
Gross profit		230,897	176,342	156,094
Operating expenses:
Research and development	[1]	90,545	106,188	53,660
Sales and marketing	[1],[2]	123,573	95,783	73,511
General and administrative	[1]	83,288	97,339	47,940
Restructuring		(66)	3,525	1,785
Total operating expenses		297,340	302,835	176,896
Loss from operations		(66,443)	(126,493)	(20,802)
Interest expense		14,157	27,801	26,865
Other non-operating (income) expense, net		(3,962)	298	(7,610)
Loss before income taxes		(76,638)	(154,592)	(40,057)
Provision for (benefit from) income taxes		(2,779)	148	(16,047)
Net loss		$ (73,859)	$ (154,740)	$ (24,010)
Net loss per share, basic and diluted		$ (0.56)	$ (1.43)	$ (0.24)
Weighted-average shares used in computing basic and diluted net loss per share		131,568	107,900	100,244

[1] ^{(1) Includes stock-based compensation, net of amounts capitalized as follows:}       Year Ended December 31,   (in thousands)   2019     2018     2017   Cost of revenue   $ 3,658     $ 8,931     $ 2,503   Research and development     21,159       48,739       9,918   Sales and marketing     11,950       19,046       8,069   General and administrative     23,478       55,054       14,496   Stock-based compensation, net of amounts capitalized   $ 60,245     $ 131,770     $ 34,986  

[2] ^{(2) Includes amortization of acquisition intangible assets as follows:}       Year Ended December 31,   (in thousands)   2019     2018     2017   Cost of revenue   $ 5,365     $ 1,952     $ 2,040   Sales and marketing     3,630       2,318       2,421   Amortization of acquisition intangible assets   $ 8,995     $ 4,270     $ 4,461