ASSET RETIREMENT OBLIGATIONS (Reconciliations of Asset Retirement Obligations) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
ASSET RETIREMENT OBLIGATIONS [Abstract]
Balance at beginning of period	$ 321.1	$ 286.4	$ 315.2	$ 283.2
Liabilities incurred	19.2	10.7	21.5	11.7
Liabilities settled	(2.3)	(5.3)	(5.6)	(10.4)
Accretion expense	3.6	3.3	10.7	9.8
Revisions, net	(1.6)	3.2	(1.8)	4.0
Balance at end of period	$ 340.0	$ 298.3	$ 340.0	$ 298.3