Discontinued Operations - Summarized Results of Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense (benefit)									$ 1,251	$ 820	$ 3,582
Discontinued operations (Note 3)	$ (44)	$ (845)	$ 11	$ 1,204	$ (1,438)	$ 95	$ (46)	$ (46)
Income (loss) from discontinued operations									326	(1,435)	(6,728)
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									989	3,055	3,794
Fuel									(304)	(879)	(1,073)
Purchased power									(84)	(268)	(533)
Other operating expenses									(435)	(1,499)	(1,263)
Provision for depreciation									(96)	(109)	(378)
General taxes									(35)	(103)	(129)
Impairment of assets									0	(2,358)	(10,622)
Other expense, net									(83)	(94)	(106)
Income (Loss) from discontinued operations, before tax									(48)	(2,255)	(10,310)
Income tax expense (benefit)									61	(820)	(3,582)
Discontinued operations (Note 3)									(109)	(1,435)	(6,728)
Gain on deconsolidation, net of tax									435	0	0
Income (loss) from discontinued operations									326	(1,435)	$ (6,728)
Tax benefit from excess deferred tax liabilities			$ 32
Nondeductible portion of interest expense									$ 60	27
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)