Discontinued Operations - Summarized Results of Discontinued Operations (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)										$ (5)	$ (1,251)	$ (820)
Discontinued operations (Note 3)		$ 70	$ 2	$ (29)	$ (35)	$ 4	$ (857)	$ (9)	$ 1,188
Income (loss) from discontinued operations	[1]									8	326	(1,435)
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]
Revenues										188	989	3,055
Fuel										(140)	(304)	(879)
Purchased power										0	(84)	(268)
Other operating expenses										(63)	(435)	(1,499)
Provision for depreciation										0	(96)	(109)
General taxes										(14)	(35)	(103)
Impairment of assets										0	0	(2,358)
Pleasants economic interest										27	0	0
Other expense, net										(2)	(83)	(94)
Income (Loss) from discontinued operations, before tax										(4)	(48)	(2,255)
Income tax expense (benefit)										47	61	(820)
Discontinued operations (Note 3)										(51)	(109)	(1,435)
Gain on deconsolidation, net of tax										59	435	0
Income (loss) from discontinued operations										$ 8	$ 326	(1,435)
FES and FENOC | Discontinued Operations, Disposed of by Means Other than Sale | Pleasants Power Station
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of assets												(120)
Competitive Asset Generation Sale | Discontinued Operations, Disposed of by Means Other than Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment of assets												$ (193)

[1] Net of income tax benefit of $5 million, $1,251 million, and $820 million in 2019, 2018 and 2017, respectively.