FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Derivative Volumes) (Details) BTU in Billions	3 Months Ended	12 Months Ended
Mar. 31, 2024 BTU GWh	Dec. 31, 2023 BTU GWh
Power Contracts GWh
Derivative Volume [Line Items]
Derivative, energy measure \| GWh	5,468	1,449
Gas Contracts BBtu
Derivative Volume [Line Items]
Derivative, energy measure \| BTU	97,012	89,105

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4E
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4E

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