COMMITMENTS, GUARANTEES AND CONTINGENCIES - Narrative (Details) $ in Thousands				12 Months Ended
	Feb. 09, 2022 USD ($)	Jul. 21, 2021 USD ($)	Oct. 29, 2020 USD ($) review	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Nov. 30, 2021 USD ($)
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated				$ 815,000
Company posted collateral related to net liability positions				89,000
Collateral received				$ 27,000
Percent of face amount of debt				100.00%
Curing period				30 days
Environmental loss contingency statement of financial position extensible enumeration not disclosed flag				Environmental liabilities
Civil penalty			$ 3,860
Number of compliance reviews | review			2
Climate change
Guarantor Obligations [Line Items]
Proposed goal to reduce CO2 pollution (percent)				30.00%
Chief Executive Officer | Code of Conduct Violation, Recoupment Amount
Guarantor Obligations [Line Items]
Proposed penalty						$ 56,000
United States v. Householder, et al. | U.S. Attorney's Office
Guarantor Obligations [Line Items]
Term of DPA		3 years
Loss in period		$ 230,000
Term of payments		60 days
United States v. Householder, et al. | United States Treasury
Guarantor Obligations [Line Items]
Proposed penalty		$ 115,000
United States v. Householder, et al. | Ohio Development Service
Guarantor Obligations [Line Items]
Proposed penalty		$ 115,000
Smith v FirstEnergy Corp et al., Buldas v FirstEnergy Corp. et al., and Hudock and Cameo Countertops, Inc. v. FirstEnergy Corp. et al.
Guarantor Obligations [Line Items]
Loss contingency accrual					$ 37,500
Emmons v. FirstEnergy Corp. et al.
Guarantor Obligations [Line Items]
Loss contingency accrual					$ 37,500
Shareholder Derivative Lawsuit
Guarantor Obligations [Line Items]
Proposed penalty	$ 36,000
Settlement payment awarded	$ 180,000
Regulation of Waste Disposal
Guarantor Obligations [Line Items]
Accrual for environmental loss contingencies				$ 96,000
Environmental liabilities former gas facilities				$ 75,000
Surety Bonds (collateralized amount)
Guarantor Obligations [Line Items]
Percent of face amount of debt				60.00%
Capped portion of surety bond obligations				$ 39,000
FE
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated				515,000
Other Assurances
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated				$ 300,000