CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (unaudited) - USD ($) shares in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenue		$ 90,941,000	$ 75,139,000	$ 179,206,000	$ 143,780,000
Cost of revenue	[1],[2]	21,009,000	19,047,000	40,953,000	36,577,000
Gross profit		69,932,000	56,092,000	138,253,000	107,203,000
Operating expenses:
Research and development	[1]	26,571,000	22,407,000	53,128,000	43,213,000
Sales and marketing	[1],[2]	42,578,000	29,689,000	84,669,000	55,739,000
General and administrative	[1]	21,339,000	19,746,000	43,271,000	40,302,000
Restructuring		0	0	0	(66,000)
Total operating expenses		90,488,000	71,842,000	181,068,000	139,188,000
Loss from operations		(20,556,000)	(15,750,000)	(42,815,000)	(31,985,000)
Interest expense		2,422,000	3,647,000	5,508,000	7,306,000
Other non-operating (income) expense, net		102,000	(575,000)	(1,134,000)	(2,554,000)
Loss before income taxes		(23,080,000)	(18,822,000)	(47,189,000)	(36,737,000)
Benefit from income taxes		(156,000)	(344,000)	(15,000)	(482,000)
Net loss		$ (22,924,000)	$ (18,478,000)	$ (47,174,000)	$ (36,255,000)
Net loss per share, basic and diluted		$ (0.17)	$ (0.14)	$ (0.34)	$ (0.28)
Weighted-average shares used in computing basic and diluted net loss per share		138,777	131,099	137,844	128,943

[1] ⁽¹⁾       Includes stock-based compensation, net of amounts capitalized as follows:       Three Months Ended June 30,     Six Months Ended June 30,   (in thousands)   2020     2019     2020     2019   Cost of revenue   $ 1,047     $ 991     $ 2,007     $ 2,087   Research and development     7,496       5,629       13,953       10,395   Sales and marketing     4,841       3,016       9,184       5,796   General and administrative     6,087       5,518       11,829       11,987   Stock-based compensation, net of amounts capitalized   $ 19,471     $ 15,154     $ 36,973     $ 30,265  

[2] ⁽²⁾      Includes amortization of acquisition intangible assets as follows:       Three Months Ended June 30,     Six Months Ended June 30,   (in thousands)   2020     2019     2020     2019   Cost of revenue   $ 2,003     $ 1,403     $ 4,013     $ 1,891   Sales and marketing     1,355       766       2,713       1,303   Amortization of acquisition intangible assets   $ 3,358     $ 2,169     $ 6,726     $ 3,194