Condensed Consolidated Statements of Operations (unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenue		$ 261,072	$ 247,047	$ 500,938	$ 475,738
Cost of revenue	[1]	132,484	119,795	253,243	224,956
Gross profit		128,588	127,252	247,695	250,782
Operating expenses:
Research and development	[1]	41,081	38,989	79,360	78,616
Sales and marketing	[1]	46,107	43,714	92,787	86,749
General and administrative	[1]	13,206	21,135	32,627	42,164
Amortization of identified intangibles		11,526	11,752	23,664	22,530
Restructuring and other		3,024	3,671	7,678	4,589
Total operating expenses		114,944	119,261	236,116	234,648
Income from operations		13,644	7,991	11,579	16,134
Interest expense		(4,989)	(4,966)	(9,943)	(9,626)
Interest income and other income (expense), net		(355)	755	934	1,042
Income before income taxes		8,300	3,780	2,570	7,550
Provision for income taxes		(4,532)	(1,021)	(2,397)	(4)
Net income		$ 3,768	$ 2,759	$ 173	$ 7,546
Net income per basic common share (in usd per share)		$ 0.08	$ 0.06	$ 0.00	$ 0.16
Net income per diluted common share (in usd per share)		$ 0.08	$ 0.06	$ 0.00	$ 0.16
Shares used in basic per-share calculation (in shares)		44,691	46,429	44,860	46,490
Shares used in diluted per-share calculation (in shares)		45,439	47,150	45,461	47,199

[1] Includes stock-based compensation expense as follows: Three Months EndedJune 30, Six Months Ended June 30, 2018 2017 2018 2017Cost of revenue$1,043 $665 $1,811 $1,499Research and development3,513 2,346 5,868 5,916Sales and marketing2,591 1,773 4,390 4,068General and administrative4,638 2,829 6,486 6,410