Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements and Derivatives (Detail Textuals)

v3.10.0.1
Fair Value Measurements and Derivatives (Detail Textuals)
$ in Millions, € in Billions
9 Months Ended
Sep. 30, 2018
USD ($)
Metric_Ton
Sep. 30, 2018
EUR (€)
Metric_Ton
Dec. 31, 2017
USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Fair value of long-term debt $ 6,693.9   $ 6,448.6
Fair value of long-term debt in excess of carrying value $ 13.9   $ 23.5
Fuel swaps      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Derivative maturing date Dec. 31, 2020    
Projected fuel purchases | Metric_Ton 0.9 0.9  
Foreign Currency Forward Contracts      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Notional amount of derivatives $ 2,300.0 € 2  
Interest Rate Swap      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Notional amount of derivatives $ 1,000.0