Annual report pursuant to Section 13 and 15(d)

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Fair Values of Pension Plan Assets) (Details)

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PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Fair Values of Pension Plan Assets) (Details) - USD ($)
$ in Millions
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets $ 215.6 $ 202.4 $ 193.4
Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 749.8 685.8 700.6
Equity Securities [Member] | U S Large Cap [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 130.1 144.7  
Equity Securities [Member] | U S Small Mid Cap [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 35.5 39.9  
Equity Securities [Member] | International [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 160.9 111.8  
Fixed Income Investments [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 202.4 181.2  
Hedge Funds [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 37.4 40.6 40.7
Hedge Funds [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 37.4 40.6  
Private Equity Funds [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 39.8 36.1 33.1
Private Equity Funds [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 39.8 36.1  
Structured Finance [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 72.9 63.8 62.1
Structured Finance [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 72.9 63.8  
Real Estate [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 65.5 61.9 $ 57.5
Real Estate [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 65.5 61.9  
Cash [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 5.3 5.8  
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 505.4 459.7  
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | U S Large Cap [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 130.1 144.7  
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | U S Small Mid Cap [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 35.5 39.9  
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | International [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 160.9 111.8  
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fixed Income Investments [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 173.6 157.5  
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Hedge Funds [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Private Equity Funds [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Structured Finance [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Real Estate [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Cash [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 5.3 5.8  
Fair Value, Inputs, Level 2 [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 28.8 23.7  
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | U S Large Cap [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | U S Small Mid Cap [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | International [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Fair Value, Inputs, Level 2 [Member] | Fixed Income Investments [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 28.8 23.7  
Fair Value, Inputs, Level 2 [Member] | Hedge Funds [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Fair Value, Inputs, Level 2 [Member] | Private Equity Funds [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Fair Value, Inputs, Level 2 [Member] | Structured Finance [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Fair Value, Inputs, Level 2 [Member] | Real Estate [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Fair Value, Inputs, Level 2 [Member] | Cash [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Significant Unobservable Inputs (Level 3) [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 215.6 202.4  
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | U S Large Cap [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | U S Small Mid Cap [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | International [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Investments [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 0.0 0.0  
Significant Unobservable Inputs (Level 3) [Member] | Hedge Funds [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 37.4 40.6  
Significant Unobservable Inputs (Level 3) [Member] | Private Equity Funds [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 39.8 36.1  
Significant Unobservable Inputs (Level 3) [Member] | Structured Finance [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 72.9 63.8  
Significant Unobservable Inputs (Level 3) [Member] | Real Estate [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets 65.5 61.9  
Significant Unobservable Inputs (Level 3) [Member] | Cash [Member] | Pension Benefits [Member]      
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Fair value of plan assets $ 0.0 $ 0.0