Accumulated Other Comprehensive Income - Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income before reclassifications						$ (97)
Amounts reclassified from AOCI	$ (7)		$ (17)		$ (13)	(34)
Deconsolidation of FES and FENOC						5
Other comprehensive loss	(7)		(17)		(13)	(126)
Income taxes (benefits) on other comprehensive income (loss)	(2)		(4)		(3)	(57)
Other comprehensive loss, net of tax	(5)	$ (5)	(13)	$ (56)	(10)	(69)
Gains & Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(10)	(11)	(15)	(22)	(11)	(22)
Other comprehensive income before reclassifications						0
Amounts reclassified from AOCI	0		2		1	4
Deconsolidation of FES and FENOC						13
Other comprehensive loss	0		2		1	17
Income taxes (benefits) on other comprehensive income (loss)	0		1		0	9
Other comprehensive loss, net of tax	0		1		1	8
Ending Balance	(10)	(10)	(14)	(15)	(10)	(14)
Unrealized Gains on AFS Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	0	0	0	67	0	67
Other comprehensive income before reclassifications						(97)
Amounts reclassified from AOCI	0		0		0	(1)
Deconsolidation of FES and FENOC						(8)
Other comprehensive loss	0		0		0	(106)
Income taxes (benefits) on other comprehensive income (loss)	0		0		0	(39)
Other comprehensive loss, net of tax	0		0		0	(67)
Ending Balance	0	0	0	0	0	0
Defined Benefit Pension & OPEB Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	46	52	101	97	52	97
Other comprehensive income before reclassifications						0
Amounts reclassified from AOCI	(7)		(19)		(14)	(37)
Deconsolidation of FES and FENOC						0
Other comprehensive loss	(7)		(19)		(14)	(37)
Income taxes (benefits) on other comprehensive income (loss)	(2)		(5)		(3)	(27)
Other comprehensive loss, net of tax	(5)		(14)		(11)	(10)
Ending Balance	41	46	87	101	41	87
AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	36	41	86	142	41	142
Other comprehensive loss, net of tax	(5)	(5)	(13)	(56)
Ending Balance	$ 31	$ 36	$ 73	$ 86	$ 31	$ 73