Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Beginning Balance	$ 142	$ 174
Other comprehensive income before reclassifications	(97)	32
Amounts reclassified from AOCI	(17)	(31)
Deconsolidation of FES and FENOC	5
Other comprehensive income (loss)	(109)	1
Income taxes (benefits) on other comprehensive income (loss)	(53)	0
Other comprehensive income (loss), net of tax	(56)	1
AOCI Ending Balance	86	175
Gains & Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Beginning Balance	(22)	(28)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from AOCI	2	3
Deconsolidation of FES and FENOC	13
Other comprehensive income (loss)	15	3
Income taxes (benefits) on other comprehensive income (loss)	8	1
Other comprehensive income (loss), net of tax	7	2
AOCI Ending Balance	(15)	(26)
Unrealized Gains on AFS Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Beginning Balance	67	52
Other comprehensive income before reclassifications	(97)	32
Amounts reclassified from AOCI	(1)	(16)
Deconsolidation of FES and FENOC	(8)
Other comprehensive income (loss)	(106)	16
Income taxes (benefits) on other comprehensive income (loss)	(39)	5
Other comprehensive income (loss), net of tax	(67)	11
AOCI Ending Balance	0	63
Defined Benefit Pension & OPEB Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Beginning Balance	97	150
Other comprehensive income before reclassifications	0	0
Amounts reclassified from AOCI	(18)	(18)
Deconsolidation of FES and FENOC	0
Other comprehensive income (loss)	(18)	(18)
Income taxes (benefits) on other comprehensive income (loss)	(22)	(6)
Other comprehensive income (loss), net of tax	4	(12)
AOCI Ending Balance	$ 101	$ 138