COMMITMENTS AND CONTINGENCIES (Mine Reclamation) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Dec. 31, 2023
Four Corners
Jointly Owned Utility Plant Interests [Line Items]
Reclamation anticipated costs	$ 6
San Juan
Jointly Owned Utility Plant Interests [Line Items]
Reclamation anticipated costs	38
Increase in other noncurrent liabilities	15
San Juan and Four Corners \| Other Noncurrent Liabilities
Jointly Owned Utility Plant Interests [Line Items]
Reclamation costs accrued	$ 42	$ 29

Total anticipated costs associated with remediation, site restoration, postclosure, monitoring commitments, or other exit costs that may occur on the sale, disposal, or abandonment of a particular property resulting from unanticipated contamination of the assets.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 5.Y.Q4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480102/450-20-S99-1

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