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 Comprehensive Income [Abstract]
Net earnings	$ 494,150us-gaap_NetIncomeLoss	$ 448,636us-gaap_NetIncomeLoss	$ 420,536us-gaap_NetIncomeLoss
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments (net of tax of $0 in 2014, 2013, and 2012)	(18,683)	(7,354)	3,522
Change in marketable securities (net of tax of $0 in 2014, 2013, and 2012)	(254)	98	39
Comprehensive income	$ 475,213us-gaap_ComprehensiveIncomeNetOfTax	$ 441,380us-gaap_ComprehensiveIncomeNetOfTax	$ 424,097us-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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