Annual report pursuant to Section 13 and 15(d)

PENSIONS AND POSTRETIREMENT BENEFITS (Effect of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) on Changes in Pension Plan Assets) (Details)

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PENSIONS AND POSTRETIREMENT BENEFITS (Effect of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) on Changes in Pension Plan Assets) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year $ 215.6 $ 202.4
Actual return on plan assets:    
Relating to assets still held at the reporting date 12.5 16.1
Purchases 5.2 57.9
Sales 8.2 65.6
Fair value of plan assets — end of year 229.1 215.6
Hedge Funds [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 37.4 40.6
Actual return on plan assets:    
Relating to assets still held at the reporting date (0.2) 2.5
Purchases 0.0 39.0
Sales 0.0 45.1
Fair value of plan assets — end of year 37.2 37.4
Private Equity Funds [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 39.8 36.1
Actual return on plan assets:    
Relating to assets still held at the reporting date 1.4 0.3
Purchases 5.2 4.5
Sales 7.8 5.6
Fair value of plan assets — end of year 42.6 39.8
Structured Finance [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 72.9 63.8
Actual return on plan assets:    
Relating to assets still held at the reporting date 5.9 9.1
Purchases 0.0 0.0
Sales 0.0 0.0
Fair value of plan assets — end of year 78.8 72.9
Real Estate [Member]    
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year 65.5 61.9
Actual return on plan assets:    
Relating to assets still held at the reporting date 5.4 4.2
Purchases 0.0 14.4
Sales 0.4 14.9
Fair value of plan assets — end of year $ 70.5 $ 65.5