FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Carrying Amount | Publicly traded debt
Liabilities:
Long-term debt	$ 8,694.3	$ 8,203.2
Carrying Amount | Non-publicly traded debt
Liabilities:
Long-term debt	24.4	277.3
Fair Value | Publicly traded debt
Liabilities:
Long-term debt	8,954.0	8,735.8
Fair Value | Non-publicly traded debt
Liabilities:
Long-term debt	23.6	270.7
Fair Value Measurements on a Recurring Basis | Fair Value
Assets:
Deferred compensation plan assets	55.0	61.1
Net investment hedge asset	2.6	1.5
Total assets, fair value	57.6	62.6
Liabilities:
Deferred compensation plan liabilities	65.6	76.9
Net investment hedge liability	4.7
Total liabilities, fair value	70.3	76.9
Fair Value Measurements on a Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Deferred compensation plan assets	29.6	29.9
Total assets, fair value	29.6	29.9
Liabilities:
Deferred compensation plan liabilities	65.6	76.9
Total liabilities, fair value	65.6	76.9
Fair Value Measurements on a Recurring Basis | Significant Other Observable Inputs (Level 2)
Assets:
Deferred compensation plan assets	25.4	31.2
Net investment hedge asset	2.6	1.5
Total assets, fair value	28.0	32.7
Liabilities:
Net investment hedge liability	4.7
Total liabilities, fair value	4.7	0.0
Cost basis of investment funds	56.7	54.8
Fair Value Measurements on a Recurring Basis | Significant Unobservable Inputs (Level 3)
Assets:
Total assets, fair value	0.0	0.0
Liabilities:
Total liabilities, fair value	$ 0.0	$ 0.0