PENSION AND POST-RETIREMENT BENEFITS - Fair Value of Asset Categories (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 432.4	$ 497.2
Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	360.6	410.9
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	159.7	194.8
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	200.9	216.1
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Investments measured at Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	71.8	86.3
Common and preferred stock | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.0	18.3
Common and preferred stock | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.0	18.3
Common and preferred stock | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and preferred stock | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Corporate Bonds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.6	17.7
Mutual Funds, Corporate Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.6	17.7
Mutual Funds, Corporate Bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Corporate Bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Government Bonds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13.4	8.4
Mutual Funds, Government Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13.4	8.4
Mutual Funds, Government Bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Government Bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, U.S. Large Cap Equiy | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	0.1
Mutual Funds, U.S. Large Cap Equiy | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	0.1
Mutual Funds, U.S. Large Cap Equiy | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, U.S. Large Cap Equiy | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, International Equities | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9.4	3.8
Mutual Funds, International Equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9.4	3.8
Mutual Funds, International Equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, International Equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Emerging Markets International Equity | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.3	7.4
Mutual Funds, Emerging Markets International Equity | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.3	7.4
Mutual Funds, Emerging Markets International Equity | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Emerging Markets International Equity | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Cash and Cash Equivalents | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.2
Mutual Funds, Cash and Cash Equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.2
Mutual Funds, Cash and Cash Equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0
Mutual Funds, Cash and Cash Equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0
Mutual Funds, Other | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.8	4.5
Mutual Funds, Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.8	4.5
Mutual Funds, Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income Securities, Corporate Bonds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		46.7
Fixed Income Securities, Corporate Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Fixed Income Securities, Corporate Bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		46.7
Fixed Income Securities, Corporate Bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0.0
Fixed Income Securities, Government Bonds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	70.0	15.4
Fixed Income Securities, Government Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income Securities, Government Bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	70.0	15.4
Fixed Income Securities, Government Bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, Corporate Bonds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40.7	49.8
Common and Collective Funds, Corporate Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19.6	27.3
Common and Collective Funds, Corporate Bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21.1	22.5
Common and Collective Funds, Corporate Bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, Government Bonds | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	43.0	44.1
Common and Collective Funds, Government Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.6	7.4
Common and Collective Funds, Government Bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	36.4	36.7
Common and Collective Funds, Government Bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, U.S. Large Cap Equity | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	54.5	68.7
Common and Collective Funds, U.S. Large Cap Equity | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.8	55.1
Common and Collective Funds, U.S. Large Cap Equity | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.7	13.6
Common and Collective Funds, U.S. Large Cap Equity | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, U.S. Small/Mid Cap Equity | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.9	16.1
Common and Collective Funds, U.S. Small/Mid Cap Equity | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.9	16.1
Common and Collective Funds, U.S. Small/Mid Cap Equity | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, U.S. Small/Mid Cap Equity | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, International Equities | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	58.4	75.7
Common and Collective Funds, International Equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.5	5.7
Common and Collective Funds, International Equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52.9	70.0
Common and Collective Funds, International Equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, Emerging Markets International Equity | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.9	18.3
Common and Collective Funds, Emerging Markets International Equity | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8.5	10.6
Common and Collective Funds, Emerging Markets International Equity | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.4	7.7
Common and Collective Funds, Emerging Markets International Equity | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, Cash and Cash Equivalents | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.7	4.2
Common and Collective Funds, Cash and Cash Equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.7	4.2
Common and Collective Funds, Cash and Cash Equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, Cash and Cash Equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, Other | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(1.6)	3.5
Common and Collective Funds, Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and Collective Funds, Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(1.6)	3.5
Common and Collective Funds, Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Cash and other investments | Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22.2	8.2
Cash and other investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	22.2	8.2
Cash and other investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Cash and other investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Common and collective funds | Investments measured at Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	36.3	37.5
Hedge funds | Investments measured at Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 35.5	$ 48.8