Fair Value Measurements (Details) (USD $)
Mar. 31, 2015
Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Convertible Debt, Fair Value Disclosures $ 432,300,000 $ 408,000,000
Convertible Debt 340,411,000 337,986,000
Fair Value, Measurements, Recurring [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Foreign Currency Contract, Asset, Fair Value Disclosure 68,452,000 41,151,000
Foreign Currency Contracts, Liability, Fair Value Disclosure (63,249,000) (36,439,000)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Foreign Currency Contract, Asset, Fair Value Disclosure 0 0
Foreign Currency Contracts, Liability, Fair Value Disclosure 0 0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Foreign Currency Contract, Asset, Fair Value Disclosure 68,452,000 41,151,000
Foreign Currency Contracts, Liability, Fair Value Disclosure (63,249,000) (36,439,000)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Foreign Currency Contract, Asset, Fair Value Disclosure 0 0
Foreign Currency Contracts, Liability, Fair Value Disclosure $ 0 $ 0