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ASSET RETIREMENT OBLIGATIONS
 3 Months Ended
Mar. 31, 2026
Asset Retirement Obligation Disclosure [Abstract]  
ASSET RETIREMENT OBLIGATIONS ASSET RETIREMENT OBLIGATIONS
Asset retirement obligations (AROs) are legal obligations associated with the retirement of long-lived assets resulting from the acquisition, construction, development and/or normal use of the underlying assets, including legal obligations for land reclamation. Recognition of a liability for an ARO is required in the period in which it is incurred at its estimated fair value. The associated asset retirement costs are capitalized as part of the carrying amount of the underlying asset and depreciated over the estimated useful life of the asset. The ARO liability is accreted through charges to operating expenses. If the ARO liability is settled for a value other than the carrying amount of the liability, we recognize a gain or loss on settlement.
ARO operating costs related to accretion of the liabilities and depreciation of the assets are as follows:
Three Months Ended
March 31
in millions20262025
ARO Operating Costs
Accretion$5.0 $4.3 
Depreciation3.7 3.9 
Total ARO operating costs$8.7 $8.2 
ARO operating costs are reported in cost of revenues. ARO liabilities are reported within other noncurrent liabilities in our accompanying Condensed Consolidated Balance Sheets.
Reconciliations of the carrying amounts of our ARO liabilities are as follows:
Three Months Ended
March 31
in millions20262025
Asset Retirement Obligations
ARO liability balance at beginning of period
$456.5 $427.4 
Liabilities incurred0.0 0.0 
Liabilities settled
(3.0)(5.9)
Accretion expense5.0 4.3 
Revisions, net
1.5 3.7 
ARO liability balance at end of period
$460.0 $429.5