CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue		$ 95,429	$ 79,317	$ 274,635	$ 223,097
Cost of revenue	[1],[2]	21,899	19,626	62,852	56,203
Gross profit		73,530	59,691	211,783	166,894
Operating expenses:
Research and development	[1]	30,068	22,718	83,196	65,931
Sales and marketing	[1],[2]	43,875	30,926	128,544	86,665
General and administrative	[1]	22,181	20,992	65,452	61,294
Restructuring		0	0	0	(66)
Total operating expenses		96,124	74,636	277,192	213,824
Loss from operations		(22,594)	(14,945)	(65,409)	(46,930)
Interest expense		2,379	3,572	7,887	10,878
Other non-operating income, net		(143)	(887)	(1,277)	(3,441)
Loss before income taxes		(24,830)	(17,630)	(72,019)	(54,367)
Provision for (benefit from) income taxes		1,289	(1,320)	1,274	(1,802)
Net loss		$ (26,119)	$ (16,310)	$ (73,293)	$ (52,565)
Net loss per share, basic and diluted		$ (0.19)	$ (0.12)	$ (0.53)	$ (0.40)
Weighted-average shares used in computing basic and diluted net loss per share		141,034	133,417	138,907	130,434

[1] ⁽¹⁾       Includes stock-based compensation, net of amounts capitalized as follows:       Three Months Ended September 30,     Nine Months Ended September 30,   (in thousands)   2020     2019     2020     2019   Cost of revenue   $ 1,222     $ 718     $ 3,229     $ 2,805   Research and development     8,322       5,468       22,275       15,863   Sales and marketing     5,912       2,918       15,096       8,714   General and administrative     6,150       5,678       17,979       17,665   Stock-based compensation, net of amounts capitalized   $ 21,606     $ 14,782     $ 58,579     $ 45,047  

[2] ⁽²⁾      Includes amortization of acquisition intangible assets as follows:       Three Months Ended September 30,     Nine Months Ended September 30,   (in thousands)   2020     2019     2020     2019   Cost of revenue   $ 1,800     $ 1,557     $ 5,813     $ 3,448   Sales and marketing     1,270       964       3,983       2,267   Amortization of acquisition intangible assets   $ 3,070     $ 2,521     $ 9,796     $ 5,715