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DERIVATIVE INSTRUMENTS - GAINS (LOSSES) AND NOTIONAL VOLUMES (Details) MWh in Millions, MMBTU in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025 USD ($) MMBTU MWh	Sep. 30, 2024 USD ($) MWh MMBTU	Sep. 30, 2025 USD ($) MMBTU MWh	Sep. 30, 2024 USD ($) MWh MMBTU
Realized gains and losses
Gains (losses)	$ (7.0)	$ (20.0)	$ 2.4	$ (103.1)
Natural gas contracts
Realized gains and losses
Gains (losses)	$ (13.6)	$ (24.0)	$ (9.0)	$ (110.7)
Notional sales volumes
Notional sales volumes | MMBTU	37.6	38.6	146.4	154.5
FTRs and TCRs
Realized gains and losses
Gains (losses)	$ 6.6	$ 4.0	$ 11.4	$ 7.6
Notional sales volumes
Notional sales volumes | MWh	6.8	7.9	21.2	23.1

X

- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-SubTopic 10
-Topic 825
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482881/825-10-55-10

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- References

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X

- Definition

Nominal energy measure used to calculate payments on a derivative instrument.

+ References

No definition available.

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- References

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