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, 2016
Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]    
Fair value of plan assets — beginning of year $ 193.4 $ 188.1
Actual return on plan assets:    
Relating to assets still held at the reporting date 12.3 5.5
Purchases 8.0 5.7
Sales 14.6 8.4
Fair value of plan assets — end of year 202.4 193.4
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 40.7 41.5
Actual return on plan assets:    
Relating to assets still held at the reporting date (0.1) (0.8)
Purchases 0.0 0.0
Sales 0.0 0.0
Fair value of plan assets — end of year 40.6 40.7
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 33.1 31.2
Actual return on plan assets:    
Relating to assets still held at the reporting date (2.7) 1.5
Purchases 8.0 5.7
Sales 6.0 7.8
Fair value of plan assets — end of year 36.1 33.1
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 62.1 65.4
Actual return on plan assets:    
Relating to assets still held at the reporting date 10.0 (3.3)
Purchases 0.0 0.0
Sales 8.0 0.0
Fair value of plan assets — end of year 63.8 62.1
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 57.5 50.0
Actual return on plan assets:    
Relating to assets still held at the reporting date 5.1 8.1
Purchases 0.0 0.0
Sales 0.6 0.6
Fair value of plan assets — end of year $ 61.9 $ 57.5