INCOME TAXES (Components of Net Deferred Income Tax Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
INCOME TAXES [Abstract]
Operating lease liabilities	$ 139.1	$ 149.7
Asset retirement obligations & other reserves	87.1	82.5
State net operating losses	79.6	86.3
Incentive compensation	57.6	62.1
State bonus depreciation	54.7	41.4
Employee benefits	22.9	14.2
Other	82.3	72.0
Total gross deferred tax assets	523.3	508.2
Valuation allowance	(89.5)	(76.8)
Total net deferred tax asset	433.8	431.4
Property, plant & equipment	907.1	889.4
Goodwill/other intangible assets	334.4	379.2
Operating lease right-of-use assets	128.2	143.6
Other	93.0	92.0
Total deferred tax liabilities	1,462.7	1,504.2
Deferred income tax liability, net	$ 1,028.9	$ 1,072.8