Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Revenue		$ 228,694	$ 197,674	$ 625,969	$ 579,327
Cost of revenue	[1]	112,409	88,877	295,841	263,782
Gross profit		116,285	108,797	330,128	315,545
Operating expenses:
Research and development	[1]	36,125	33,840	103,913	100,563
Sales and marketing	[1]	39,814	36,113	114,117	107,902
General and administrative	[1]	18,223	17,617	54,210	49,973
Restructuring and other (Note 11)		584	3,021	2,544	5,662
Amortization of identified intangibles		8,759	5,284	18,120	15,266
Total operating expenses		103,505	95,875	292,904	279,366
Income from operations		12,780	12,922	37,224	36,179
Interest expense		(4,634)	(1,070)	(12,870)	(1,635)
Interest income and other expense, net		(645)	(5,000)	(1,046)	(4,720)
Income before income taxes		7,501	6,852	23,308	29,824
Benefit from (provision for) income taxes		2,756	(2,047)	(97)	(8,025)
Net income		$ 10,257	$ 4,805	$ 23,211	$ 21,799
Net income per basic common share		$ 0.22	$ 0.10	$ 0.49	$ 0.47
Net income per diluted common share		$ 0.21	$ 0.10	$ 0.48	$ 0.45
Shares used in basic per-share calculation		47,473	46,904	47,104	46,829
Shares used in diluted per-share calculation		48,501	48,184	48,161	48,304

[1] Includes stock-based compensation expense as follows: 2015 2014 2015 2014 Cost of revenue $ 785 $ 780 $ 2,357 $ 1,894 Research and development 2,397 2,316 7,749 6,482 Sales and marketing 1,891 1,486 6,461 4,069 General and administrative 4,455 4,452 11,520 12,706