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, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]
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
Purchases	57.9	8.0
Sales	65.6	14.6
Fair value of plan assets — end of year	215.6	202.4
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	40.6	40.7
Actual return on plan assets:
Relating to assets still held at the reporting date	2.5	(0.1)
Purchases	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]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Roll Forward]
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)
Purchases	4.5	8.0
Sales	5.6	6.0
Fair value of plan assets — end of year	39.8	36.1
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	63.8	62.1
Actual return on plan assets:
Relating to assets still held at the reporting date	9.1	10.0
Purchases	0.0	0.0
Sales	0.0	8.0
Fair value of plan assets — end of year	72.9	63.8
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	61.9	57.5
Actual return on plan assets:
Relating to assets still held at the reporting date	4.2	5.1
Purchases	14.4	0.0
Sales	14.9	0.6
Fair value of plan assets — end of year	$ 65.5	$ 61.9

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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

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- Definition

Amount of increase in plan assets of defined benefit plan from business combination.

+ 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 (b)(6)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Amount of decrease in plan assets of defined benefit plan from disposal or classification as held-for-sale.

+ 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 (b)(7)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ 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 (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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