CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 120,807us-gaap_ProfitLoss	$ 121,274us-gaap_ProfitLoss	$ 477,186us-gaap_ProfitLoss
Other comprehensive loss:
Foreign currency translation	(10,872)	(2,740)
Change in unrealized gain on marketable securities	1,349	1,306
Other	759	239
Total other comprehensive loss	(8,764)	(1,195)	(6,538)
Comprehensive income	112,043	120,079
Comprehensive income attributable to noncontrolling interest	365	227
Comprehensive income attributable to common stockholders	$ 111,678us-gaap_ComprehensiveIncomeNetOfTax	$ 119,852us-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 of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), attributable to noncontrolling interests. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax, before 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 and reclassification adjustments of other comprehensive income (loss).

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

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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