Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 77,746us-gaap_NetIncomeLoss	$ 72,800us-gaap_NetIncomeLoss
Other comprehensive (loss) income:
Foreign currency translation adjustments	(8,415)	1,367
Change in unrealized gain (loss) on investments, net of income tax (provision) benefit of $(1,213) and $123 for the three months ended March 31, 2015 and 2014, respectively	2,113	(913)
Other comprehensive (loss) income	(6,302)	454
Comprehensive income	$ 71,444us-gaap_ComprehensiveIncomeNetOfTax	$ 73,254us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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