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REGULATORY MATTERS - Pennsylvania and West Virginia (Details) $ in Millions													3 Months Ended	6 Months Ended		12 Months Ended
	Jul. 27, 2026 MW	Jul. 02, 2026	May 15, 2026 USD ($)	Feb. 18, 2026 USD ($) MW	Feb. 13, 2026 MW	Nov. 26, 2025 USD ($)	Oct. 01, 2025 MW	Aug. 29, 2025 USD ($)	Jul. 11, 2025	Jan. 17, 2025	May 01, 2022 MW	Feb. 24, 2022	Mar. 31, 2026 USD ($)	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)
Regulatory Matters [Line Items]
Charges incurred														$ 145.0	$ 0.0
PJM \| Subsequent Event
Regulatory Matters [Line Items]
Amount of energy looking to be procured (in MW's) \| MW	6,800
Transmission Related Vegetation Management Programs \| FERC \| FE
Regulatory Matters [Line Items]
Utilities, transmission owning utilities join an RTO												0.00500000
Transmission Related Vegetation Management Programs \| FERC \| FE \| Subsequent Event
Regulatory Matters [Line Items]
Utilities, transmission owning utilities join an RTO		0.0050
Transmission ROE Incentive \| FERC
Regulatory Matters [Line Items]
Utilities, transmission owing utilities join an RTO										0.00500000
Public utilities, amount awarded from other party																$ 46.0
Estimated refund obligation														79.0
Transmission ROE Incentive \| FERC \| Income Statement Location [Axis]: us-gaap:OtherNonoperatingIncomeExpense
Regulatory Matters [Line Items]
Public utilities, amount awarded from other party																4.0
Transmission ROE Incentive \| FERC \| Transmission \| Income Statement Location [Axis]: us-gaap:Revenues
Regulatory Matters [Line Items]
Public utilities, amount awarded from other party																$ 42.0
Transmission ROE Incentive \| FERC \| ATSI \| Subsequent Event
Regulatory Matters [Line Items]
Request to remove basis point adder	0.00500000
PJM 2024 RTEP Window 1 \| Valley Link Transmission Rate
Regulatory Matters [Line Items]
Recovery of project abandonment costs (percent)									50.00%
Recovery of project abandonment costs incurred thereafter (percent)									100.00%
Pennsylvania \| EE&C Phase IV \| PPUC
Regulatory Matters [Line Items]
Public utilities, approved energy consumption reduction targets, cost recovery														$ 390.0
Pennsylvania \| EE&C Phase IV \| PPUC \| ME
Regulatory Matters [Line Items]
Demand reduction targets														2.90%
Energy consumption reduction targets														3.10%
Pennsylvania \| EE&C Phase IV \| PPUC \| PN
Regulatory Matters [Line Items]
Demand reduction targets														3.30%
Energy consumption reduction targets														3.00%
Pennsylvania \| EE&C Phase IV \| PPUC \| Penn
Regulatory Matters [Line Items]
Demand reduction targets														2.00%
Energy consumption reduction targets														2.70%
Pennsylvania \| EE&C Phase IV \| PPUC \| WP
Regulatory Matters [Line Items]
Demand reduction targets														2.50%
Energy consumption reduction targets														2.40%
Pennsylvania \| Energy Efficiency and Conservation Phase V \| PPUC
Regulatory Matters [Line Items]
Public utilities, approved energy consumption reduction targets, cost recovery						$ 390,000.0
Pennsylvania \| Energy Efficiency and Conservation Phase V \| PPUC \| FE PA
Regulatory Matters [Line Items]
Demand reduction targets						2.01%
Energy consumption reduction targets						2.00%
West Virginia \| WVPSC \| MP and PE
Regulatory Matters [Line Items]
Charges incurred													$ 145.0
West Virginia \| WVPSC \| MP and PE \| Solar Generation Project
Regulatory Matters [Line Items]
Percent of subscriptions required prior to commencement of construction											85.00%
Plant capacity (in MW's) \| MW											50
Amount of requested increase (decrease)			$ 188,400.0					$ (3.2)
Public utilities, near-term market capacity purchases (in MV's) \| MW				70	70		70
Public utilities, increase in total revenues, percentage			10.60%
Amount of requested base rate increase			$ 174.6
Amount of requested surcharge rate increase			13.8
West Virginia \| WVPSC \| MP and PE \| Natural Gas Generation Project
Regulatory Matters [Line Items]
Public utilities, near-term market capacity purchases (in MV's) \| MW				1,200	1,200		1,200
Public utilities, requested rate increase, estimated initial investment				$ 2,700.0
West Virginia \| Requested Approach Effective August 1, 2026 \| WVPSC \| MP and PE \| Solar Generation Project
Regulatory Matters [Line Items]
Amount of requested increase (decrease)			37.9
West Virginia \| Requested Approach Effective June 1, 2027 \| WVPSC \| MP and PE \| Solar Generation Project
Regulatory Matters [Line Items]
Amount of requested increase (decrease)			$ 37.6