Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Beginning Balance	$ 41	$ 142
Other comprehensive income before reclassifications		(97)
Amounts reclassified from AOCI	(6)	(17)
Other comprehensive loss	(6)	(109)
Income taxes (benefits) on other comprehensive income (loss)	(1)	(53)
Other comprehensive loss, net of tax	(5)	(56)
AOCI Ending Balance	36	86
Gains & Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Beginning Balance	(11)	(22)
Other comprehensive income before reclassifications		0
Amounts reclassified from AOCI	1	2
Deconsolidation of FES and FENOC		13
Other comprehensive loss	1	15
Income taxes (benefits) on other comprehensive income (loss)	0	8
Other comprehensive loss, net of tax	1	7
AOCI Ending Balance	(10)	(15)
Unrealized Gains on AFS Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Beginning Balance	0	67
Other comprehensive income before reclassifications		(97)
Amounts reclassified from AOCI	0	(1)
Deconsolidation of FES and FENOC		(8)
Other comprehensive loss	0	(106)
Income taxes (benefits) on other comprehensive income (loss)	0	(39)
Other comprehensive loss, net of tax	0	(67)
AOCI Ending Balance	0	0
Defined Benefit Pension & OPEB Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
AOCI Beginning Balance	52	97
Other comprehensive income before reclassifications		0
Amounts reclassified from AOCI	(7)	(18)
Deconsolidation of FES and FENOC		0
Other comprehensive loss	(7)	(18)
Income taxes (benefits) on other comprehensive income (loss)	(1)	(22)
Other comprehensive loss, net of tax	(6)	4
AOCI Ending Balance	46	101
AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Deconsolidation of FES and FENOC		5
Other comprehensive loss, net of tax	$ (5)	$ (56)