COMMITMENTS, GUARANTEES AND CONTINGENCIES - Narrative (Details) $ in Thousands				12 Months Ended
	Feb. 09, 2022 USD ($)	Jul. 21, 2021 USD ($)	Oct. 29, 2020 USD ($) review	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Nov. 30, 2021 USD ($)
Loss Contingencies [Line Items]
Outstanding guarantees and other assurances aggregated				$ 1,000,000
Company posted collateral related to net liability positions				50,000
Collateral received				$ 206,000
Civil penalty			$ 3,860
Number of compliance reviews | review			2
EnvironmentalLossContingencyStatementOfFinancialPositionExtensibleEnumerationNotDisclosedFlag				The settlement also includes a payment to FE
Other Assurances
Loss Contingencies [Line Items]
Outstanding guarantees and other assurances aggregated				$ 449,000
FE
Loss Contingencies [Line Items]
Outstanding guarantees and other assurances aggregated				$ 528,000
Climate change
Loss Contingencies [Line Items]
Proposed reduction in power plants carbon pollution (percent)				30.00%
Code of Conduct Violation, Recoupment Amount | Chief Executive Officer
Loss Contingencies [Line Items]
Proposed penalty						$ 56,000
Smith v FirstEnergy Corp et al., Buldas v FirstEnergy Corp. et al., and Hudock and Cameo Countertops, Inc. v. FirstEnergy Corp. et al.
Loss Contingencies [Line Items]
Loss contingency accrual					$ 37,500
Emmons v. FirstEnergy Corp. et al.
Loss Contingencies [Line Items]
Loss contingency accrual					$ 37,500
Shareholder Derivative Lawsuit
Loss Contingencies [Line Items]
Proposed penalty	$ 36,000
Settlement payment awarded	$ 180,000
U.S. Attorney's Office | United States v. Householder, et al.
Loss Contingencies [Line Items]
Term of DPA		3 years
Loss in period		$ 230,000
Term of payments		60 days
United States Treasury | United States v. Householder, et al.
Loss Contingencies [Line Items]
Proposed penalty		$ 115,000
Ohio Development Service | United States v. Householder, et al.
Loss Contingencies [Line Items]
Proposed penalty		$ 115,000
Regulation of Waste Disposal
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies				$ 97,000
Environmental liabilities former gas facilities				$ 62,000