DISCONTINUED OPERATIONS - Narrative (Details) $ in Millions		1 Months Ended	3 Months Ended			12 Months Ended
	Feb. 27, 2020 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2019 MW
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Worthless stock deduction	$ 4,900		$ 5,200
Unrecognized tax benefits from worthless stock deduction	316					$ 81
Worthless stock deduction, net of tax			1,100
Increase in NOL allocation				$ 289
Increase in NOL allocation tax effected			61
State and Local
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Worthless stock deduction, net of tax			$ 21
Disposal Group, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from asset sales					$ 65
AE Supply | Purchase Agreement with Subsidiary of LS Power | Pleasants Power Station
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Plant generation capacity (in MW's) | MW							1,300
IT Access Agreement | Affiliated companies | FES
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount paid to settle claims	$ 125
FES Key Creditor Groups | Affiliated companies | FES
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Settlement of claims upon emergence		$ 853