Annual report pursuant to Section 13 and 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
12 Months Ended
Dec. 31, 2018
USD ($)
Metric_Ton
Dec. 31, 2018
EUR (€)
Metric_Ton
Dec. 31, 2017
USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Fair value of long-term debt $ 6,601.9   $ 6,448.6
Fair value of long-term debt in excess of carrying value $ 8.4   $ 23.5
Fuel contracts      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Projected fuel purchases | Metric_Ton 1.3 1.3  
Derivative maturing date Dec. 31, 2021    
Foreign currency forward contracts      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Notional amount of derivatives $ 2,400.0 € 2.1  
Interest rate contracts      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Notional amount of derivatives $ 1,000.0