PENSION AND POST-RETIREMENT PLANS - FAIR VALUE (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension and Post-retirement Plans
Total	$ 162.2	$ 186.7	$ 178.8
Significant Unobservable Inputs (Level 3) | Private equity partnership interests
Pension and Post-retirement Plans
Total		0.1	$ 0.1
Fair Value Measurement
Pension and Post-retirement Plans
Total	162.3	186.7
Fair Value Measurement | Cash
Pension and Post-retirement Plans
Total	6.2	6.6
Fair Value Measurement | U.S. large-cap
Pension and Post-retirement Plans
Total	50.6	66.0
Fair Value Measurement | U.S. mid- and small-cap
Pension and Post-retirement Plans
Total	38.4	42.6
Fair Value Measurement | International large-cap
Pension and Post-retirement Plans
Total	18.0	21.6
Fair Value Measurement | International small-cap
Pension and Post-retirement Plans
Total	8.1	9.5
Fair Value Measurement | U.S. Treasuries
Pension and Post-retirement Plans
Total	8.0	8.0
Fair Value Measurement | Municipal bonds
Pension and Post-retirement Plans
Total	0.1	0.1
Fair Value Measurement | Investment grade U.S. corporate bonds
Pension and Post-retirement Plans
Total	20.8	17.5
Fair Value Measurement | High-yield U.S. corporate bonds
Pension and Post-retirement Plans
Total	0.5	3.6
Fair Value Measurement | Real estate partnerships interests
Pension and Post-retirement Plans
Total	11.6	11.1
Fair Value Measurement | Private equity partnership interests
Pension and Post-retirement Plans
Total		0.1
Fair Value Measurement | Quoted Prices in Active Markets (Level 1)
Pension and Post-retirement Plans
Total	56.9	63.0
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) | Cash
Pension and Post-retirement Plans
Total	6.2	6.6
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) | U.S. large-cap
Pension and Post-retirement Plans
Total	24.9	28.1
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) | U.S. mid- and small-cap
Pension and Post-retirement Plans
Total	25.8	28.3
Fair Value Measurement | Significant Observable Inputs (Level 2)
Pension and Post-retirement Plans
Total	93.8	112.5
Fair Value Measurement | Significant Observable Inputs (Level 2) | U.S. large-cap
Pension and Post-retirement Plans
Total	25.7	37.9
Fair Value Measurement | Significant Observable Inputs (Level 2) | U.S. mid- and small-cap
Pension and Post-retirement Plans
Total	12.6	14.3
Fair Value Measurement | Significant Observable Inputs (Level 2) | International large-cap
Pension and Post-retirement Plans
Total	18.0	21.6
Fair Value Measurement | Significant Observable Inputs (Level 2) | International small-cap
Pension and Post-retirement Plans
Total	8.1	9.5
Fair Value Measurement | Significant Observable Inputs (Level 2) | U.S. Treasuries
Pension and Post-retirement Plans
Total	8.0	8.0
Fair Value Measurement | Significant Observable Inputs (Level 2) | Municipal bonds
Pension and Post-retirement Plans
Total	0.1	0.1
Fair Value Measurement | Significant Observable Inputs (Level 2) | Investment grade U.S. corporate bonds
Pension and Post-retirement Plans
Total	20.8	17.5
Fair Value Measurement | Significant Observable Inputs (Level 2) | High-yield U.S. corporate bonds
Pension and Post-retirement Plans
Total	0.5	3.6
Fair Value Measurement | Significant Unobservable Inputs (Level 3)
Pension and Post-retirement Plans
Total	11.6	11.2
Fair Value Measurement | Significant Unobservable Inputs (Level 3) | Real estate partnerships interests
Pension and Post-retirement Plans
Total	$ 11.6	11.1
Fair Value Measurement | Significant Unobservable Inputs (Level 3) | Private equity partnership interests
Pension and Post-retirement Plans
Total		$ 0.1