RATE MATTERS - FERC Annual Revenue Requirements (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended	57 Months Ended
Sep. 30, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2025
FERC 2021 PJM and SPP Transmission Formula Rate Challenge
Public Utilities, General Disclosures [Line Items]
Stand alone treatment of nolcs annual revenue increase	$ 48.7	$ 52.1	$ 60.7	$ 68.5	$ 78.3	$ 308.3

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