Consolidated Statements of Income - 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	$ 551,030	$ 498,042	$ 1,618,289	$ 1,427,579
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	183,204	158,812	532,408	447,742
Research and development	38,396	32,583	110,917	92,869
Sales and marketing	107,426	96,215	322,406	268,742
General and administrative	99,543	81,905	288,287	239,946
Amortization of acquired intangible assets	6,752	8,403	20,284	23,654
Restructuring charges (benefits)	20	(115)	517	1,189
Total costs and operating expenses	435,341	377,803	1,274,819	1,074,142
Income from operations	115,689	120,239	343,470	353,437
Interest income	2,723	2,010	8,265	5,389
Interest expense	(4,630)	(4,482)	(13,884)	(10,939)
Other income (expense), net	204	(188)	(1,702)	(1,968)
Income before provision for income taxes	113,986	117,579	336,149	345,919
Provision for income taxes	25,946	26,424	103,163	109,078
Net income	$ 88,040	$ 91,155	$ 232,986	$ 236,841
Net income per share:
Basic (in dollars per share)	$ 0.49	$ 0.51	$ 1.30	$ 1.33
Diluted (in dollars per share)	$ 0.49	$ 0.50	$ 1.29	$ 1.31
Shares used in per share calculations:
Basic (in shares)	178,547	178,186	178,591	178,324
Diluted (in shares)	180,364	180,955	180,642	181,278