INCOME TAXES (Components of Net Deferred Income Tax Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
INCOME TAXES [Abstract]
Employee benefits	$ 11.8	$ 21.9
Incentive compensation	62.5	58.2
Asset retirement obligations & other reserves	77.9	58.3
State net operating losses	75.0	67.7
Other	59.1	25.4
Total gross deferred tax assets	286.3	231.5
Valuation allowance	(53.3)	(32.5)
Total net deferred tax asset	233.0	199.0
Property, plant & equipment	794.3	622.9
Goodwill/other intangible assets	380.2	252.2
Other	64.4	30.0
Total deferred tax liabilities	1,238.9	905.1
Net deferred tax liability	$ 1,005.9	$ 706.1