Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements and Derivatives (Detail Textuals)

v3.2.0.727
Fair Value Measurements and Derivatives (Detail Textuals)
€ in Millions, NOK in Millions, $ in Millions
 6 Months Ended
Jun. 30, 2015
USD ($)
Metric_Ton
Jun. 30, 2015
EUR (€)
Metric_Ton
Jun. 30, 2015
NOK
Metric_Ton
Dec. 31, 2014
USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Fair value of long-term debt $ 5,812.0     $ 6,229.1
Fair value of long-term debt in excess of carrying value $ 48.9     $ 45.0
Fuel Swaps        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Derivative maturing date Dec. 31, 2018      
Projected fuel purchases | Metric_Ton 1,100,000 1,100,000 1,100,000  
Fuel Swaps | Not Designated as Hedging Instrument        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Projected fuel purchases | Metric_Ton 100,000 100,000 100,000  
Interest Rate Swap        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Notional amount of derivatives $ 1,200.0      
Foreign Currency Forward Contracts        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Notional amount of derivatives 1,000.0 € 900.0    
Notional amount of derivatives 15.9   NOK 124.8  
Foreign Currency Collar        
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]        
Notional amount of derivatives $ 305.9 € 274.4