ASSET RETIREMENT OBLIGATIONS (Tables)

12 Months Ended

Dec. 31, 2023

ASSET RETIREMENT OBLIGATIONS [Abstract]

Asset Retirement Obligations Operating Costs

in millions	2023	2022	2021
ARO Operating Costs
Accretion	$         13.9	$         14.1	$         13.1
Depreciation	9.0	9.4	10.6
Total	$         22.9	$         23.5	$         23.7

Reconciliations of Asset Retirement Obligations

in millions	2023	2022
Asset Retirement Obligations
Balance at beginning of year	$       311.3	$       315.2
Liabilities incurred	0.0	8.2
Liabilities settled	(9.9)	(8.8)
Accretion expense	13.9	14.1
Revisions, net	8.8	(17.4)
Balance at end of year	$       324.1	$       311.3