Pension and Other Postemployment Benefits - Narrative (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
	Feb. 01, 2019	Jan. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Mark-to-market adjustment, net of capitalized amounts			$ 676	$ 145	$ 141
Increase in discount rate			1.10%
Company contributions	$ 500
Funding contributions made for current and future years		$ 750
Pensions and OPEB
Defined Benefit Plan Disclosure [Line Items]
Actual return on plan assets			$ 1,492	$ 371	$ 999
Actual return on plan assets (percent)			20.20%	(4.00%)	15.10%
Expected return on plan assets			$ 569	$ 605	$ 478
Pension
Defined Benefit Plan Disclosure [Line Items]
Company contributions			521	1,270
Actual return on plan assets			$ 1,419	$ (363)
Expected long-term return on plan assets			7.50%	7.50%	7.50%
Expected return on plan assets			$ 540	$ 574	$ 448
Increase in benefit obligation due to RP2014 mortality table			29
Net periodic benefit costs (credits)			703	287	$ 265
Excluded from total investments			176	68
OPEB
Defined Benefit Plan Disclosure [Line Items]
Company contributions			21	22
Actual return on plan assets			$ 73	$ (8)
Expected long-term return on plan assets			7.50%	7.50%	7.50%
Expected return on plan assets			$ 29	$ 31	$ 30
Increase in benefit obligation due to RP2014 mortality table			3
Net periodic benefit costs (credits)			(20)	(156)	(66)
Excluded from total investments			1	(2)
Minimum
Defined Benefit Plan Disclosure [Line Items]
Company contributions		$ 500
Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Mark-to-market adjustment, net of capitalized amounts			2	1	39
FES and FENOC | Discontinued Operations, Disposed of by Means Other than Sale
Defined Benefit Plan Disclosure [Line Items]
Expenses from transactions with related parties			37	42
FES and FENOC | Discontinued Operations, Disposed of by Means Other than Sale | Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit costs (credits)			242	64	60
FES and FENOC | Discontinued Operations, Disposed of by Means Other than Sale | OPEB
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit costs (credits)			$ (19)	$ (25)	$ (17)