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)
Metric_Ton in Millions, $ in Millions, € in Billions
6 Months Ended
Jun. 30, 2018
USD ($)
Metric_Ton
Jun. 30, 2018
EUR (€)
Metric_Ton
Dec. 31, 2017
USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Fair value of long-term debt $ 6,964.9   $ 6,448.6
Fair value of long-term debt in excess of carrying value $ 4.2   $ 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 1.0 1.0  
Foreign Currency Forward Contracts      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Notional amount of derivatives $ 1,800.0 € 1.5  
Interest Rate Swap      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Notional amount of derivatives $ 1,000.0