PENSION AND POST-RETIREMENT BENEFITS - Fair Value of Asset Categories (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 462.4	$ 432.4
Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	377.4	360.6
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	179.0	159.7
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	198.4	200.9
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	85.0	71.8
U.S. Small/Mid Cap Equity | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	7.0
U.S. Small/Mid Cap Equity | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	7.0
U.S. Small/Mid Cap Equity | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. Small/Mid Cap Equity | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Corporate Bonds | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.8	10.6
Mutual Funds, Corporate Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.8	10.6
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.8	13.4
Mutual Funds, Government Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.8	13.4
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	0.2
Mutual Funds, U.S. Large Cap Equiy | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.2	0.2
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.3	9.4
Mutual Funds, International Equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.3	9.4
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.9	5.3
Mutual Funds, Emerging Markets International Equity | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.9	5.3
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.6	2.2
Mutual Funds, Cash and Cash Equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.6	2.2
Mutual Funds, Cash and Cash Equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Cash and Cash Equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Mutual Funds, Other | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.0	1.8
Mutual Funds, Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.0	1.8
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income Securities, Corporate Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income Securities, Corporate Bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income Securities, Corporate Bonds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income Securities, Government Bonds | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	72.2	70.0
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	72.2	70.0
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33.6	40.7
Common and Collective Funds, Corporate Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19.4	19.6
Common and Collective Funds, Corporate Bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.2	21.1
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.9	43.0
Common and Collective Funds, Government Bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9.1	6.6
Common and Collective Funds, Government Bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29.8	36.4
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55.5	54.5
Common and Collective Funds, U.S. Large Cap Equity | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.7	38.8
Common and Collective Funds, U.S. Large Cap Equity | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.8	15.7
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18.2	6.9
Common and Collective Funds, U.S. Small/Mid Cap Equity | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18.2	6.9
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	70.8	58.4
Common and Collective Funds, International Equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.4	5.5
Common and Collective Funds, International Equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	67.4	52.9
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18.1	14.9
Common and Collective Funds, Emerging Markets International Equity | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13.0	8.5
Common and Collective Funds, Emerging Markets International Equity | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.1	6.4
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.7	1.7
Common and Collective Funds, Cash and Cash Equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.7	1.7
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 | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2.9	(1.6)
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	2.9	(1.6)
Common and Collective Funds, Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Cash and Cash Equivalents | Total
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12.9	22.2
Cash and Cash Equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12.9	22.2
Cash and Cash Equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
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 | Investments measured at Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	52.4	36.3
Hedge Funds | Investments measured at Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 32.6	$ 35.5