Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement [Abstract]
Revenue	$ 540,723	$ 476,035	$ 1,067,259	$ 929,537
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	179,910	149,318	349,204	288,930
Research and development	36,693	32,052	72,521	60,286
Sales and marketing	111,501	91,462	214,980	172,527
General and administrative	99,152	81,880	188,744	158,041
Amortization of acquired intangible assets	6,752	8,403	13,532	15,251
Restructuring charges	455	569	497	1,304
Total costs and operating expenses	434,463	363,684	839,478	696,339
Income from operations	106,260	112,351	227,781	233,198
Interest income	2,541	1,740	5,542	3,379
Interest expense	(4,678)	(4,516)	(9,254)	(6,457)
Other expense, net	(1,605)	(899)	(1,906)	(1,780)
Income before provision for income taxes	102,518	108,676	222,163	228,340
Provision for income taxes	35,318	35,790	77,217	82,654
Net income	$ 67,200	$ 72,886	$ 144,946	$ 145,686
Net income per share:
Basic (in dollars per share)	$ 0.38	$ 0.41	$ 0.81	$ 0.82
Diluted (in dollars per share)	$ 0.37	$ 0.40	$ 0.80	$ 0.80
Shares used in per share calculations:
Basic (in shares)	178,682	178,081	178,614	178,393
Diluted (in shares)	180,738	180,841	180,782	181,439