Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Revenue	$ 526,536us-gaap_Revenues	$ 453,502us-gaap_Revenues
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	169,294us-gaap_CostOfRevenue	139,612us-gaap_CostOfRevenue
Research and development	35,828us-gaap_ResearchAndDevelopmentExpense	28,234us-gaap_ResearchAndDevelopmentExpense
Sales and marketing	103,479us-gaap_SellingAndMarketingExpense	81,065us-gaap_SellingAndMarketingExpense
General and administrative	89,592us-gaap_GeneralAndAdministrativeExpense	76,161us-gaap_GeneralAndAdministrativeExpense
Amortization of acquired intangible assets	6,780us-gaap_AmortizationOfIntangibleAssets	6,848us-gaap_AmortizationOfIntangibleAssets
Restructuring charges	42us-gaap_RestructuringCharges	735us-gaap_RestructuringCharges
Total costs and operating expenses	405,015us-gaap_CostsAndExpenses	332,655us-gaap_CostsAndExpenses
Income from operations	121,521us-gaap_OperatingIncomeLoss	120,847us-gaap_OperatingIncomeLoss
Interest income	3,001us-gaap_InvestmentIncomeInterest	1,639us-gaap_InvestmentIncomeInterest
Interest expense	(4,576)us-gaap_InterestExpense	(1,941)us-gaap_InterestExpense
Other expense, net	(301)us-gaap_OtherNonoperatingIncomeExpense	(881)us-gaap_OtherNonoperatingIncomeExpense
Income before provision for income taxes	119,645	119,664
Provision for income taxes	41,899us-gaap_IncomeTaxExpenseBenefit	46,864us-gaap_IncomeTaxExpenseBenefit
Net income	$ 77,746us-gaap_NetIncomeLoss	$ 72,800us-gaap_NetIncomeLoss
Net income per share:
Basic (in dollars per share)	$ 0.44us-gaap_EarningsPerShareBasic	$ 0.41us-gaap_EarningsPerShareBasic
Diluted (in dollars per share)	$ 0.43us-gaap_EarningsPerShareDiluted	$ 0.40us-gaap_EarningsPerShareDiluted
Shares used in per share calculations:
Basic (in shares)	178,545	178,705
Diluted (in shares)	180,825	182,038

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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