Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements and Derivatives - Derivatives measured at fair value and discloses balance sheet location (Details)

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Fair Value Measurements and Derivatives - Derivatives measured at fair value and discloses balance sheet location (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Derivatives, Fair Value [Line Items]    
Derivative assets, fair value $ 118,195 $ 20,302
Derivative liabilities, fair value 45,523 238,069
Fuel swaps | Designated as Hedging Instrument | Prepaid expenses and other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, fair value 5,796 20,288
Fuel swaps | Designated as Hedging Instrument | Other long-term assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, fair value 4,636  
Derivative liabilities, fair value 1,903  
Fuel swaps | Designated as Hedging Instrument | Accrued expenses and other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative assets, fair value 4,237  
Derivative liabilities, fair value 26,069 44,271
Fuel swaps | Designated as Hedging Instrument | Other long-term liabilities    
Derivatives, Fair Value [Line Items]    
Derivative assets, fair value 7,724 13,237
Derivative liabilities, fair value 17,578 38,608
Foreign currency forward contracts | Designated as Hedging Instrument | Prepaid expenses and other assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, fair value 41,983  
Derivative liabilities, fair value 1,354  
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term assets    
Derivatives, Fair Value [Line Items]    
Derivative assets, fair value 65,780 14
Foreign currency forward contracts | Designated as Hedging Instrument | Accrued expenses and other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, fair value   61,788
Foreign currency forward contracts | Designated as Hedging Instrument | Other long-term liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, fair value   88,920
Interest rate swaps | Designated as Hedging Instrument | Accrued expenses and other liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, fair value $ 1,876 3,331
Interest rate swaps | Designated as Hedging Instrument | Other long-term liabilities    
Derivatives, Fair Value [Line Items]    
Derivative liabilities, fair value   $ 1,151