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Financial Instruments, Risk Management and Fair Value Measurements - Narrative (Details)
MMBTU in Millions, $ in Millions
Mar. 31, 2018
USD ($)
MMBTU
Dec. 31, 2017
USD ($)
Derivative [Line Items]    
Estimated fair value of debt $ 3,364.7 $ 3,250.6
Carrying value of debt 3,322.1 $ 3,185.6
Designated as Hedging Instrument | Foreign exchange contracts    
Derivative [Line Items]    
Derivative notional amount $ 352.6  
Designated as Hedging Instrument | Energy contracts    
Derivative [Line Items]    
Nonmonetary notional amount of price risk cash flow hedge (in mmBTUs) | MMBTU 0.0  
Designated as Hedging Instrument | Foreign Currency and Energy Contracts    
Derivative [Line Items]    
Cumulative changes in net gain (loss) from cash flow hedges $ 6.1  
Not Designated as Hedging Instruments | Foreign exchange contracts    
Derivative [Line Items]    
Derivative notional amount 1,628.6  
Designated as Cash Flow Hedges | Designated as Hedging Instrument | Foreign exchange contracts    
Derivative [Line Items]    
Cumulative changes in net gain (loss) from cash flow hedges $ 6.1