FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Carrying Amount | Publicly traded debt
Liabilities:
Long-term debt	$ 8,265.3	$ 8,203.2
Carrying Amount | Non-publicly traded debt
Liabilities:
Long-term debt	25.7	277.3
Fair Value | Publicly traded debt
Liabilities:
Long-term debt	9,440.1	8,735.8
Fair Value | Non-publicly traded debt
Liabilities:
Long-term debt	25.5	270.7
Fair Value Measurements on a Recurring Basis | Fair Value
Assets:
Deferred compensation plan assets	63.5	61.1
Net investment hedge asset		1.5
Total assets, fair value	63.5	62.6
Liabilities:
Deferred compensation plan liabilities	81.8	76.9
Net investment hedge liability	49.2
Total liabilities, fair value	131.0	76.9
Fair Value Measurements on a Recurring Basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Deferred compensation plan assets	30.7	29.9
Total assets, fair value	30.7	29.9
Liabilities:
Deferred compensation plan liabilities	81.8	76.9
Total liabilities, fair value	81.8	76.9
Fair Value Measurements on a Recurring Basis | Significant Other Observable Inputs (Level 2)
Assets:
Deferred compensation plan assets	32.8	31.2
Net investment hedge asset		1.5
Total assets, fair value	32.8	32.7
Liabilities:
Net investment hedge liability	49.2
Total liabilities, fair value	49.2	0.0
Cost basis of investment funds	56.2	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