PENSION AND POST-RETIREMENT BENEFITS - Fair Value of Asset Categories (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | $ 463 | $ 462.4 | |
Pension Plans | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 463 | 462.4 | $ 432.4 |
Pension Plans | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 387.9 | 377.4 | |
Pension Plans | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 189.7 | 179 | |
Pension Plans | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 198.2 | 198.4 | |
Pension Plans | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Investments measured at Net Asset Value | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 75.1 | 85 | |
Pension Plans | Common and preferred stock, US small/mid cap equity | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and preferred stock, US small/mid cap equity | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and preferred stock, US small/mid cap equity | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and preferred stock, US small/mid cap equity | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, Corporate Bonds | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 10.8 | 10.8 | |
Pension Plans | Mutual Funds, Corporate Bonds | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 10.8 | 10.8 | |
Pension Plans | Mutual Funds, Corporate Bonds | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, Corporate Bonds | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, Government Bonds | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 15.8 | 15.8 | |
Pension Plans | Mutual Funds, Government Bonds | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 15.8 | 15.8 | |
Pension Plans | Mutual Funds, Government Bonds | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, Government Bonds | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, U.S. Large Cap Equiy | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0.2 | |
Pension Plans | Mutual Funds, U.S. Large Cap Equiy | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0.2 | |
Pension Plans | Mutual Funds, U.S. Large Cap Equiy | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, U.S. Large Cap Equiy | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, International Equities | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 21.7 | 16.3 | |
Pension Plans | Mutual Funds, International Equities | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 21.7 | 16.3 | |
Pension Plans | Mutual Funds, International Equities | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, International Equities | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, Emerging Markets International Equity | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 1.7 | 5.9 | |
Pension Plans | Mutual Funds, Emerging Markets International Equity | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 1.7 | 5.9 | |
Pension Plans | Mutual Funds, Emerging Markets International Equity | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, Emerging Markets International Equity | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, U.S., Small/Mid Cap Equity | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 1.1 | | |
Pension Plans | Mutual Funds, U.S., Small/Mid Cap Equity | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 1.1 | | |
Pension Plans | Mutual Funds, U.S., Small/Mid Cap Equity | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | | |
Pension Plans | Mutual Funds, U.S., Small/Mid Cap Equity | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | | |
Pension Plans | Mutual Funds, Cash and Cash Equivalents | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 6 | 1.6 | |
Pension Plans | Mutual Funds, Cash and Cash Equivalents | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 6 | 1.6 | |
Pension Plans | Mutual Funds, Cash and Cash Equivalents | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, Cash and Cash Equivalents | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, Other | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 1.2 | 2 | |
Pension Plans | Mutual Funds, Other | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 1.2 | 2 | |
Pension Plans | Mutual Funds, Other | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Mutual Funds, Other | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Fixed Income Securities, Corporate Bonds | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Fixed Income Securities, Corporate Bonds | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Fixed Income Securities, Corporate Bonds | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Fixed Income Securities, Corporate Bonds | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Fixed Income Securities, Government Bonds | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 68.1 | 72.2 | |
Pension Plans | Fixed Income Securities, Government Bonds | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Fixed Income Securities, Government Bonds | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 68.1 | 72.2 | |
Pension Plans | Fixed Income Securities, Government Bonds | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, Corporate Bonds | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 34.6 | 33.6 | |
Pension Plans | Common and Collective Funds, Corporate Bonds | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 20.7 | 19.4 | |
Pension Plans | Common and Collective Funds, Corporate Bonds | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 13.9 | 14.2 | |
Pension Plans | Common and Collective Funds, Corporate Bonds | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, Government Bonds | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 38.7 | 38.9 | |
Pension Plans | Common and Collective Funds, Government Bonds | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 4.8 | 9.1 | |
Pension Plans | Common and Collective Funds, Government Bonds | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 33.9 | 29.8 | |
Pension Plans | Common and Collective Funds, Government Bonds | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, U.S. Large Cap Equity | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 59 | 55.5 | |
Pension Plans | Common and Collective Funds, U.S. Large Cap Equity | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 51 | 48.7 | |
Pension Plans | Common and Collective Funds, U.S. Large Cap Equity | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 8 | 6.8 | |
Pension Plans | Common and Collective Funds, U.S. Large Cap Equity | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, U.S. Small/Mid Cap Equity | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 24.6 | 18.2 | |
Pension Plans | Common and Collective Funds, U.S. Small/Mid Cap Equity | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 24.6 | 18.2 | |
Pension Plans | Common and Collective Funds, U.S. Small/Mid Cap Equity | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, U.S. Small/Mid Cap Equity | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, International Equities | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 72.7 | 70.8 | |
Pension Plans | Common and Collective Funds, International Equities | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 4.4 | 3.4 | |
Pension Plans | Common and Collective Funds, International Equities | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 68.3 | 67.4 | |
Pension Plans | Common and Collective Funds, International Equities | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, Emerging Markets International Equity | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 24.5 | 18.1 | |
Pension Plans | Common and Collective Funds, Emerging Markets International Equity | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 19.1 | 13 | |
Pension Plans | Common and Collective Funds, Emerging Markets International Equity | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 5.4 | 5.1 | |
Pension Plans | Common and Collective Funds, Emerging Markets International Equity | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, Cash and Cash Equivalents | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 1.8 | 1.7 | |
Pension Plans | Common and Collective Funds, Cash and Cash Equivalents | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 1.8 | 1.7 | |
Pension Plans | Common and Collective Funds, Cash and Cash Equivalents | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, Cash and Cash Equivalents | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, Other | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0.6 | 2.9 | |
Pension Plans | Common and Collective Funds, Other | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds, Other | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0.6 | 2.9 | |
Pension Plans | Common and Collective Funds, Other | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Cash and Cash Equivalents | Fair Value, Inputs, Level 1, 2 and 3 [Member] | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 5 | 12.9 | |
Pension Plans | Cash and Cash Equivalents | Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 5 | 12.9 | |
Pension Plans | Cash and Cash Equivalents | Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Cash and Cash Equivalents | Level 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 0 | 0 | |
Pension Plans | Common and Collective Funds | Investments measured at Net Asset Value | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | 45.9 | 52.4 | |
Pension Plans | Hedge Funds | Investments measured at Net Asset Value | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Plan Assets at Fair Value | $ 29.2 | $ 32.6 | |