REGULATORY MATTERS - Pennsylvania and West Virginia (Details) $ in Thousands								3 Months Ended	6 Months Ended
	May 31, 2023 USD ($)	Jan. 13, 2023 USD ($)	Aug. 25, 2022 USD ($) MW	May 01, 2022 USD ($)	Mar. 17, 2022	Nov. 22, 2021 site MW	Jan. 16, 2020 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2023 USD ($) proposal
FERC | Regulated Transmission
Regulatory Matters [Line Items]
Pre-tax impairment of regulatory asset								$ 25,000	$ 25,000
FERC | Transmission Related Vegetation Management Programs | FirstEnergy
Regulatory Matters [Line Items]
Customer refund								45,000
Customer refund, net								34,000
Capital assets								195,000
Operating expense								90,000
Operating expense, net								67,000
Reduction in operating expense								$ 160,000
Pennsylvania | DSP June 2019- May 2023
Regulatory Matters [Line Items]
Number of RFP's | proposal									2
RFP term									2 years
Pennsylvania | Three month period | DSP June 2019- May 2023
Regulatory Matters [Line Items]
Term of energy contract									3 months
Pennsylvania | Twelve month period | DSP June 2019- May 2023
Regulatory Matters [Line Items]
Term of energy contract									12 months
Pennsylvania | Twenty-four month period | DSP June 2019- May 2023
Regulatory Matters [Line Items]
Term of energy contract									24 months
Pennsylvania | Pennsylvania Companies | PPUC | New LTIIPs
Regulatory Matters [Line Items]
Recovery period							5 years
Amount of requested rate increase (decrease)							$ 572,000
Pennsylvania | ME | PPUC | EE&C Phase IV
Regulatory Matters [Line Items]
Demand reduction targets								2.90%	2.90%
Energy consumption reduction targets								3.10%	3.10%
Pennsylvania | PN | PPUC | EE&C Phase IV
Regulatory Matters [Line Items]
Demand reduction targets								3.30%	3.30%
Energy consumption reduction targets								3.00%	3.00%
Pennsylvania | Penn | PPUC | EE&C Phase IV
Regulatory Matters [Line Items]
Demand reduction targets								2.00%	2.00%
Energy consumption reduction targets								2.70%	2.70%
Pennsylvania | WP | PPUC | EE&C Phase IV
Regulatory Matters [Line Items]
Demand reduction targets								2.50%	2.50%
Energy consumption reduction targets								2.40%	2.40%
West Virginia | MP and PE | WVPSC
Regulatory Matters [Line Items]
Amount of requested rate increase (decrease)	$ 207,000
Requested amount of annual depreciation expense	$ 76,000	$ 76,000
Regulatory staff requested increase in annual amount of depreciation expense		33,400
Consumer advocate requested increase in annual amount of depreciation expense		$ 300
West Virginia | MP and PE | WVPSC | ENEC
Regulatory Matters [Line Items]
Amount of requested rate increase (decrease)			$ 183,800
Under recovered amount, percent			12.20%
Supplemental requested decrease			$ 145,000
Approved amount of annual increase			$ 92,000
Approved ROE			4.00%
Plant capacity (in MW's) | MW			1,200
West Virginia | MP and PE | WVPSC | Solar Generation Project
Regulatory Matters [Line Items]
Plant capacity (in MW's) | MW						50
Percent of subscriptions required prior to commencement of construction					85.00%
Number of proposed solar sites | site						3
Number of solar sites | site						5
Expected cost of the program				$ 110,000