FAIR VALUE MEASUREMENTS (Details 2) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Long-term Debt, Fair Value	$ 3,736.9	$ 3,911.0	$ 3,912.2
Notes Payable	3,535.4	3,612.0	3,612.6
Fair Value, Inputs, Level 1
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Long-term Debt, Fair Value	0.0	0.0	0.0
Fair Value, Inputs, Level 2
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Long-term Debt, Fair Value	3,583.9	3,758.0	3,759.2
Fair Value, Inputs, Level 3
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Long-term Debt, Fair Value	$ 153.0	$ 153.0	$ 153.0