FAIR VALUE MEASUREMENTS (Details 2) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Long-term Debt, Fair Value	$ 4,177.2	$ 3,572.7
Debt, Long-term and Short-term, Combined Amount	3,863.8	3,340.8
Quoted Prices In Active Markets for Identical Assets (Level 1)
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Long-term Debt, Fair Value	0.0	0.0
Significant Other Observable Inputs (Level 2)
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Long-term Debt, Fair Value	4,177.2	3,572.7
Significant Unobservable Inputs (Level 3)
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Long-term Debt, Fair Value	$ 0.0	$ 0.0