CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenue		$ 254,324	$ 218,773	$ 207,295
Cost of revenue	[1],[2]	77,982	62,679	67,755
Gross profit		176,342	156,094	139,540
Operating expenses:
Research and development	[2]	106,188	53,660	37,985
Sales and marketing	[1],[2]	95,783	73,511	73,970
General and administrative	[2]	97,339	47,940	36,832
Restructuring	[2]	3,525	1,785	25,256
Total operating expenses		302,835	176,896	174,043
Loss from operations		(126,493)	(20,802)	(34,503)
Interest expense		27,801	26,865	32,893
Other non-operating income (expense), net		(298)	7,610	(4,250)
Loss before income taxes		(154,592)	(40,057)	(71,646)
Provision for (benefit from) income taxes		148	(16,047)	4,704
Net loss		$ (154,740)	$ (24,010)	$ (76,350)
Net loss per share, basic and diluted		$ (1.43)	$ (0.24)	$ (0.77)
Weighted-average shares used in computing basic and diluted net loss per share		107,900	100,244	98,539

[1] Includes amortization of acquisition intangible assets as follows: Year Ended December 31, (in thousands) 2018 2017 2016 Cost of revenue $1,952 $2,040 $4,505 Sales and marketing 2,318 2,421 4,267 Amortization of acquisition intangible assets $4,270 $4,461 $8,772

[2] Includes stock-based compensation, net of amounts capitalized as follows: Year Ended December 31, (in thousands) 2018 2017 2016 Cost of revenue $8,931 $2,503 $4,114 Research and development 48,739 9,918 5,756 Sales and marketing 19,046 8,069 8,712 General and administrative 55,054 14,496 12,301 Restructuring — — 2,074 Stock-based compensation, net of amounts capitalized $131,770 $34,986 $32,957