Discontinued Operations - Narrative (Details) $ in Millions			3 Months Ended
		Feb. 27, 2020 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 MW
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Worthless stock deduction		$ 4,900
Unrecognized tax benefits from worthless stock deduction		316
Worthless stock deduction, net of tax		1,100
Unrecognized tax benefits from worthless stock deduction, net of tax		72
Discontinued operations, net of tax	[1]		$ 0	$ 50
Pleasants Power Station | AE Supply | Purchase Agreement with Subsidiary of LS Power
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Plant capacity (in MW's) | MW					1,300
Discontinued Operations, Disposed of by Means Other than Sale | FES and FENOC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued operations, net of tax			$ 0	50
Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from asset sales				$ 65
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
IT Access Agreement | Affiliated Companies | FES
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Settlement of claims upon emergence		125
State and Local Jurisdiction
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Worthless stock deduction, net of tax		$ 80

[1] Net of income tax benefits of $36 million for the three months ended March 31, 2020.