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PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Fair Values of Other Benefit 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] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | $ 215.6 | $ 202.4 | $ 193.4
Hedge Funds [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 37.4 | 40.6 | 40.7
Private Equity Funds [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 39.8 | 36.1 | 33.1
Real Estate [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 65.5 | 61.9 | 57.5
Other Benefits [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 262.5 | 253.0 | 250.6
Other Benefits [Member] | Equity Securities [Member] | U S Large Cap [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 11.4 | 10.6 |
Other Benefits [Member] | Equity Securities [Member] | U S Small Mid Cap [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 2.8 | 2.7 |
Other Benefits [Member] | Equity Securities [Member] | International [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 8.8 | 8.1 |
Other Benefits [Member] | Fixed Income Investments [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 204.1 | 197.9 |
Other Benefits [Member] | Hedge Funds [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 11.4 | 11.2 |
Other Benefits [Member] | Private Equity Funds [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 3.9 | 4.3 |
Other Benefits [Member] | Structured Credit [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 7.9 | 6.9 |
Other Benefits [Member] | Real Estate [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 12.0 | 11.1 |
Other Benefits [Member] | Cash [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.2 | 0.2 |
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 187.3 | 183.6 |
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | U S Large Cap [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 11.4 | 10.6 |
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | U S Small Mid Cap [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 2.8 | 2.7 |
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Equity Securities [Member] | International [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 8.8 | 8.1 |
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Fixed Income Investments [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 164.1 | 162.0 |
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Hedge Funds [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Private Equity Funds [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Structured Credit [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Real Estate [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member] | Cash [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.2 | 0.2 |
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 40.0 | 35.9 |
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | U S Large Cap [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | U S Small Mid Cap [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] | International [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Fixed Income Investments [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 40.0 | 35.9 |
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Hedge Funds [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Private Equity Funds [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Structured Credit [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Real Estate [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Fair Value, Inputs, Level 2 [Member] | Cash [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 35.2 | 33.5 | 32.5
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | U S Large Cap [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | U S Small Mid Cap [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Equity Securities [Member] | International [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fixed Income Investments [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 0.0 | 0.0 |
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Hedge Funds [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 11.4 | 11.2 | 11.2
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Private Equity Funds [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 3.9 | 4.3 | 5.5
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Structured Credit [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 7.9 | 6.9 | 5.8
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Real Estate [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | 12.0 | 11.1 | $ 10.0
Other Benefits [Member] | Significant Unobservable Inputs (Level 3) [Member] | Cash [Member] |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Defined Benefit Plan, Fair Value of Plan Assets | $ 0.0 | $ 0.0 |

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