PENSION AND POST-RETIREMENT PLANS - FAIR VALUE (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension and Post-retirement Plans
Total	$ 194.8	$ 162.2	$ 186.7
Fair Value Measurement
Pension and Post-retirement Plans
Total	157.3	130.1
Total plan assets	194.8	162.3
Fair Value Measurement | Cash
Pension and Post-retirement Plans
Total	6.3	6.2
Fair Value Measurement | U.S. large-cap
Pension and Post-retirement Plans
Total	62.4	50.6
Fair Value Measurement | U.S. mid- and small-cap
Pension and Post-retirement Plans
Total	49.6	38.4
Fair Value Measurement | International large-cap
Pension and Post-retirement Plans
Total	6.6	5.5
Fair Value Measurement | U.S. Treasuries
Pension and Post-retirement Plans
Total	14.1	8.0
Fair Value Measurement | Municipal bonds
Pension and Post-retirement Plans
Total		0.1
Fair Value Measurement | Investment grade U.S. corporate bonds
Pension and Post-retirement Plans
Total	18.2	20.8
Fair Value Measurement | High-yield U.S. corporate bonds
Pension and Post-retirement Plans
Total	0.1	0.5
Fair Value Measurement | Quoted Prices in Active Markets (Level 1)
Pension and Post-retirement Plans
Total	63.9	56.9
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) | Cash
Pension and Post-retirement Plans
Total	6.3	6.2
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) | U.S. large-cap
Pension and Post-retirement Plans
Total	23.7	24.9
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) | U.S. mid- and small-cap
Pension and Post-retirement Plans
Total	33.9	25.8
Fair Value Measurement | Significant Observable Inputs (Level 2)
Pension and Post-retirement Plans
Total	93.4	73.2
Fair Value Measurement | Significant Observable Inputs (Level 2) | U.S. large-cap
Pension and Post-retirement Plans
Total	38.7	25.7
Fair Value Measurement | Significant Observable Inputs (Level 2) | U.S. mid- and small-cap
Pension and Post-retirement Plans
Total	15.7	12.6
Fair Value Measurement | Significant Observable Inputs (Level 2) | International large-cap
Pension and Post-retirement Plans
Total	6.6	5.5
Fair Value Measurement | Significant Observable Inputs (Level 2) | U.S. Treasuries
Pension and Post-retirement Plans
Total	14.1	8.0
Fair Value Measurement | Significant Observable Inputs (Level 2) | Municipal bonds
Pension and Post-retirement Plans
Total		0.1
Fair Value Measurement | Significant Observable Inputs (Level 2) | Investment grade U.S. corporate bonds
Pension and Post-retirement Plans
Total	18.2	20.8
Fair Value Measurement | Significant Observable Inputs (Level 2) | High-yield U.S. corporate bonds
Pension and Post-retirement Plans
Total	0.1	0.5
Fair Value Measurement | Investment measured at NAV
Pension and Post-retirement Plans
Total	$ 37.5	$ 32.2