DISCONTINUED OPERATIONS - Summarized Results of Discontinued Operations (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax benefit		$ (21)		$ (48)
Income from discontinued operations	[1]	(21)	$ 0	44
FES and FENOC | Discontinued Operations, Disposed of by Means Other than Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other expense, net		0	0	(4)
Loss from discontinued operations, before tax		0	0	(4)
Income tax benefit		0	0	(1)
Loss from discontinued operations, net of tax		0	0	(3)
Income tax expense (benefit), including worthless stock deduction		21	0	(47)
Gain (loss) on disposal, net of tax		(21)	0	47
Income from discontinued operations		$ (21)	$ 0	$ 44

[1] Net of income tax benefit (expense) of ($21 million) and $48 million in 2023 and 2021, respectively.