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           Consolidated Statements of Comprehensive Income (Loss) (USD $) 
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        12 Months Ended | |||||||||
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           Dec. 31, 2014 
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           Dec. 31, 2013 
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           Dec. 31, 2012 
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| Statement of Comprehensive Income [Abstract] | ||||||||||
| Net income | $ 247,403,000us-gaap_NetIncomeLoss | $ 153,192,000us-gaap_NetIncomeLoss | $ 68,371,000us-gaap_NetIncomeLoss | |||||||
| Foreign currency translation adjustment | (16,894,000)us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent | (12,223,000)us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent | 1,355,000us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent | |||||||
| Change in fair value of derivative instruments | 0us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax | [1] | (4,419,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax | [1] | (8,452,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax | [1] | ||||
| Reclassification of settled contracts | 0us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax | [2] | 10,290,000us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax | [2] | 1,005,000us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax | [2] | ||||
| Other comprehensive loss | (16,894,000)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent | (6,352,000)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent | (6,092,000)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent | |||||||
| Comprehensive income | 230,509,000us-gaap_ComprehensiveIncomeNetOfTax | 146,840,000us-gaap_ComprehensiveIncomeNetOfTax | 62,279,000us-gaap_ComprehensiveIncomeNetOfTax | |||||||
| Change in fair value of derivative instruments, tax | 0us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax | 4,300,000us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax | (4,300,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax | |||||||
| Reclassification of settled contracts, tax | $ 0us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax | $ (500,000)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax | $ 500,000us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax | |||||||
          
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- Definition 
          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. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          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, attributable to parent entity. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Amount after tax of other comprehensive income (loss) attributable to parent entity. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Amount after tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss). Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss). Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss). Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition 
          Amount of tax expense (benefit), before reclassification adjustments, related to increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss). Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Details 
          
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