Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 74,806us-gaap_NetIncomeLoss	$ 76,016us-gaap_NetIncomeLoss	$ 60,069us-gaap_NetIncomeLoss
Net cumulative translation adjustment and foreign currency exchange hedge, net of tax of $(275), $(310) and $(390), respectively	(399)	(537)	(748)
Net unrealized (loss) gain on securities available-for-sale, net of tax of ($9), $14, and $(244), respectively	(16)	21	(342)
Less: reclassification adjustment for realized gain on the sale of securities available-for-sale included in Other Income, net of tax of $(24), $(299) and $(76), respectively	(39)	(474)	(121)
Net changed in unrealized (loss) on securities available-for-sale, net of tax	(55)	(453)	(463)
Comprehensive Income	$ 74,352us-gaap_ComprehensiveIncomeNetOfTax	$ 75,026us-gaap_ComprehensiveIncomeNetOfTax	$ 58,858us-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 of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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

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