Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss)	$ (53)	$ 4	$ (122)
Income taxes (benefits) on other comprehensive income (loss)	(21)	1	(47)
Other comprehensive income (loss), net of tax	(32)	3	(75)
FES
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	218
Other comprehensive income (loss)	18	38	(18)
Income taxes (benefits) on other comprehensive income (loss)	6	15	(7)
Other comprehensive income (loss), net of tax	12	23	(11)
Ending Balance	(2,070)	218
Accumulated Other Comprehensive Income
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	174	171	246
Other comprehensive income before reclassifications	74	119	24
Amounts reclassified from AOCI	(127)	(115)	(146)
Other comprehensive income (loss)	(53)	4	(122)
Income taxes (benefits) on other comprehensive income (loss)	(21)	1	(47)
Other comprehensive income (loss), net of tax	(32)	3	(75)
Ending Balance	142	174	171
Accumulated Other Comprehensive Income | FES
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	69	46	57
Other comprehensive income before reclassifications	91	100	25
Amounts reclassified from AOCI	(73)	(62)	(43)
Other comprehensive income (loss)	18	38	(18)
Income taxes (benefits) on other comprehensive income (loss)	6	15	(7)
Other comprehensive income (loss), net of tax	12	23	(11)
Ending Balance	81	69	46
Gains & Losses on Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(28)	(33)	(37)
Other comprehensive income before reclassifications	0	0	0
Amounts reclassified from AOCI	10	8	5
Other comprehensive income (loss)	10	8	5
Income taxes (benefits) on other comprehensive income (loss)	4	3	1
Other comprehensive income (loss), net of tax	6	5	4
Ending Balance	(22)	(28)	(33)
Gains & Losses on Cash Flow Hedges | FES
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(9)	(9)	(7)
Other comprehensive income before reclassifications	0	0	0
Amounts reclassified from AOCI	2	0	(3)
Other comprehensive income (loss)	2	0	(3)
Income taxes (benefits) on other comprehensive income (loss)	1	0	(1)
Other comprehensive income (loss), net of tax	1	0	(2)
Ending Balance	(8)	(9)	(9)
Unrealized Gains on AFS Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	52	18	25
Other comprehensive income before reclassifications	85	106	14
Amounts reclassified from AOCI	(63)	(51)	(25)
Other comprehensive income (loss)	22	55	(11)
Income taxes (benefits) on other comprehensive income (loss)	7	21	(4)
Other comprehensive income (loss), net of tax	15	34	(7)
Ending Balance	67	52	18
Unrealized Gains on AFS Securities | FES
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	48	16	21
Other comprehensive income before reclassifications	91	100	15
Amounts reclassified from AOCI	(61)	(48)	(24)
Other comprehensive income (loss)	30	52	(9)
Income taxes (benefits) on other comprehensive income (loss)	10	20	(4)
Other comprehensive income (loss), net of tax	20	32	(5)
Ending Balance	68	48	16
Defined Benefit Pension & OPEB Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	150	186	258
Other comprehensive income before reclassifications	(11)	13	10
Amounts reclassified from AOCI	(74)	(72)	(126)
Other comprehensive income (loss)	(85)	(59)	(116)
Income taxes (benefits) on other comprehensive income (loss)	(32)	(23)	(44)
Other comprehensive income (loss), net of tax	(53)	(36)	(72)
Ending Balance	97	150	186
Defined Benefit Pension & OPEB Plans | FES
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	30	39	43
Other comprehensive income before reclassifications	0	0	10
Amounts reclassified from AOCI	(14)	(14)	(16)
Other comprehensive income (loss)	(14)	(14)	(6)
Income taxes (benefits) on other comprehensive income (loss)	(5)	(5)	(2)
Other comprehensive income (loss), net of tax	(9)	(9)	(4)
Ending Balance	$ 21	$ 30	$ 39