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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, 2017 | Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Fair value of plan assets — beginning of year | $ 202.4 | $ 193.4
Actual return on plan assets: |  |
Relating to assets still held at the reporting date | 16.1 | 12.3
Acquired through business combinations | 57.9 | 8.0
Sales | 65.6 | 14.6
Fair value of plan assets — end of year | 215.6 | 202.4
Hedge Funds [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Fair value of plan assets — beginning of year | 40.6 | 40.7
Actual return on plan assets: |  |
Relating to assets still held at the reporting date | 2.5 | (0.1)
Acquired through business combinations | 39.0 | 0.0
Sales | 45.1 | 0.0
Fair value of plan assets — end of year | 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 — beginning of year | 36.1 | 33.1
Actual return on plan assets: |  |
Relating to assets still held at the reporting date | 0.3 | (2.7)
Acquired through business combinations | 4.5 | 8.0
Sales | 5.6 | 6.0
Fair value of plan assets — end of year | 39.8 | 36.1
Real Estate [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Fair value of plan assets — beginning of year | 61.9 | 57.5
Actual return on plan assets: |  |
Relating to assets still held at the reporting date | 4.2 | 5.1
Acquired through business combinations | 14.4 | 0.0
Sales | 14.9 | 0.6
Fair value of plan assets — end of year | 65.5 | 61.9
Other Benefits [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Fair value of plan assets — beginning of year | 253.0 | 250.6
Actual return on plan assets: |  |
Fair value of plan assets — end of year | 262.5 | 253.0
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 | 11.2 |
Actual return on plan assets: |  |
Fair value of plan assets — end of year | 11.4 | 11.2
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 | 4.3 |
Actual return on plan assets: |  |
Fair value of plan assets — end of year | 3.9 | 4.3
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 | 6.9 |
Actual return on plan assets: |  |
Fair value of plan assets — end of year | 7.9 | 6.9
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 | 11.1 |
Actual return on plan assets: |  |
Fair value of plan assets — end of year | 12.0 | 11.1
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 | 33.5 | 32.5
Actual return on plan assets: |  |
Relating to assets still held at the reporting date | 7.1 | 1.9
Acquired through business combinations | 24.0 | 0.0
Sales | 25.5 | 1.0
Fair value of plan assets — end of year | 35.2 | 33.5
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 | 11.2 | 11.2
Actual return on plan assets: |  |
Relating to assets still held at the reporting date | 0.8 | 0.0
Acquired through business combinations | 17.1 | 0.0
Sales | 17.7 | 0.0
Fair value of plan assets — end of year | 11.4 | 11.2
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 | 4.3 | 5.5
Actual return on plan assets: |  |
Relating to assets still held at the reporting date | 0.9 | (0.3)
Acquired through business combinations | 1.8 | 0.0
Sales | 2.7 | 1.0
Fair value of plan assets — end of year | 3.9 | 4.3
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 | 6.9 | 5.8
Actual return on plan assets: |  |
Relating to assets still held at the reporting date | 2.0 | 1.1
Acquired through business combinations | 2.1 | 0.0
Sales | 2.1 | 0.0
Fair value of plan assets — end of year | 7.9 | 6.9
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 | 11.1 | 10.0
Actual return on plan assets: |  |
Relating to assets still held at the reporting date | 3.4 | 1.1
Acquired through business combinations | 3.0 | 0.0
Sales | 3.0 | 0.0
Fair value of plan assets — end of year | $ 12.0 | $ 11.1

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- Definition Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(iv)(02)(A) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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