Annual report pursuant to Section 13 and 15(d)

PENSION AND OTHER POSTRETIREMENT BENEFITS (Effect of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) on Changes in Other Benefit Plan Assets) (Details)

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PENSION AND OTHER POSTRETIREMENT BENEFITS (Effect of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) on Changes in Other Benefit Plan Assets) (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
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
Acquired through business combinations 5.2 57.9
Sales 8.2 65.6
Fair value of plan assets — end of year 229.1 215.6
Hedge Funds [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
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
Acquired through business combinations 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]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
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
Acquired through business combinations 5.2 4.5
Sales 7.8 5.6
Fair value of plan assets — end of year 42.6 39.8
Real Estate [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
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
Acquired through business combinations 0.0 14.4
Sales 0.4 14.9
Fair value of plan assets — end of year 70.5 65.5
Other Benefits [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Fair value of plan assets — beginning of year 262.5 253.0
Actual return on plan assets:    
Fair value of plan assets — end of year 240.2 262.5
Other Benefits [Member] | Hedge Funds [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Fair value of plan assets — beginning of year 11.4  
Actual return on plan assets:    
Fair value of plan assets — end of year 11.4 11.4
Other Benefits [Member] | Private Equity Funds [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Fair value of plan assets — beginning of year 3.9  
Actual return on plan assets:    
Fair value of plan assets — end of year 3.0 3.9
Other Benefits [Member] | Structured Credit [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Fair value of plan assets — beginning of year 7.9  
Actual return on plan assets:    
Fair value of plan assets — end of year 8.5 7.9
Other Benefits [Member] | Real Estate [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Fair value of plan assets — beginning of year 12.0  
Actual return on plan assets:    
Fair value of plan assets — end of year 13.1 12.0
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Fair value of plan assets — beginning of year 35.2 33.5
Actual return on plan assets:    
Relating to assets still held at the reporting date 1.6 7.1
Acquired through business combinations 0.0 24.0
Sales 1.1 25.5
Fair value of plan assets — end of year 36.0 35.2
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Hedge Funds [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Fair value of plan assets — beginning of year 11.4 11.2
Actual return on plan assets:    
Relating to assets still held at the reporting date 0.0 0.8
Acquired through business combinations 0.0 17.1
Sales 0.0 17.7
Fair value of plan assets — end of year 11.4 11.4
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Private Equity Funds [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Fair value of plan assets — beginning of year 3.9 4.3
Actual return on plan assets:    
Relating to assets still held at the reporting date (0.1) 0.9
Acquired through business combinations 0.0 1.8
Sales 1.1 2.7
Fair value of plan assets — end of year 3.0 3.9
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Structured Credit [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Fair value of plan assets — beginning of year 7.9 6.9
Actual return on plan assets:    
Relating to assets still held at the reporting date 0.6 2.0
Acquired through business combinations 0.0 2.1
Sales 0.0 2.1
Fair value of plan assets — end of year 8.5 7.9
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Real Estate [Member]    
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]    
Fair value of plan assets — beginning of year 12.0 11.1
Actual return on plan assets:    
Relating to assets still held at the reporting date 1.1 3.4
Acquired through business combinations 0.0 3.0
Sales 0.0 3.0
Fair value of plan assets — end of year $ 13.1 $ 12.0