Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
AOCI Beginning Balance	$ 171	$ 246	$ 284
Other comprehensive income before reclassifications	119	24	181
Amounts reclassified from AOCI	(115)	(146)	(233)
Other comprehensive income (loss)	4	(122)	(52)
Income taxes (benefits) on other comprehensive income (loss)	1	(47)	(14)
Other comprehensive income (loss), net of tax	3	(75)	(38)
AOCI Ending Balance	174	171	246
FES
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
AOCI Beginning Balance	46	57	54
Other comprehensive income before reclassifications	100	25	93
Amounts reclassified from AOCI	(62)	(43)	(88)
Other comprehensive income (loss)	38	(18)	5
Income taxes (benefits) on other comprehensive income (loss)	15	(7)	2
Other comprehensive income (loss), net of tax	23	(11)	3
AOCI Ending Balance	69	46	57
Gains & Losses on Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
AOCI Beginning Balance	(33)	(37)	(36)
Other comprehensive income before reclassifications	0	0	0
Amounts reclassified from AOCI	8	5	(2)
Other comprehensive income (loss)	8	5	(2)
Income taxes (benefits) on other comprehensive income (loss)	3	1	(1)
Other comprehensive income (loss), net of tax	5	4	(1)
AOCI Ending Balance	(28)	(33)	(37)
Gains & Losses on Cash Flow Hedges | FES
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
AOCI Beginning Balance	(9)	(7)	(1)
Other comprehensive income before reclassifications	0	0	0
Amounts reclassified from AOCI	0	(3)	(10)
Other comprehensive income (loss)	0	(3)	(10)
Income taxes (benefits) on other comprehensive income (loss)	0	(1)	(4)
Other comprehensive income (loss), net of tax	0	(2)	(6)
AOCI Ending Balance	(9)	(9)	(7)
Unrealized Gains on AFS Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
AOCI Beginning Balance	18	25	9
Other comprehensive income before reclassifications	106	14	89
Amounts reclassified from AOCI	(51)	(25)	(63)
Other comprehensive income (loss)	55	(11)	26
Income taxes (benefits) on other comprehensive income (loss)	21	(4)	10
Other comprehensive income (loss), net of tax	34	(7)	16
AOCI Ending Balance	52	18	25
Unrealized Gains on AFS Securities | FES
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
AOCI Beginning Balance	16	21	8
Other comprehensive income before reclassifications	100	15	80
Amounts reclassified from AOCI	(48)	(24)	(59)
Other comprehensive income (loss)	52	(9)	21
Income taxes (benefits) on other comprehensive income (loss)	20	(4)	8
Other comprehensive income (loss), net of tax	32	(5)	13
AOCI Ending Balance	48	16	21
Defined Benefit Pension & OPEB Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
AOCI Beginning Balance	186	258	311
Other comprehensive income before reclassifications	13	10	92
Amounts reclassified from AOCI	(72)	(126)	(168)
Other comprehensive income (loss)	(59)	(116)	(76)
Income taxes (benefits) on other comprehensive income (loss)	(23)	(44)	(23)
Other comprehensive income (loss), net of tax	(36)	(72)	(53)
AOCI Ending Balance	150	186	258
Defined Benefit Pension & OPEB Plans | FES
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
AOCI Beginning Balance	39	43	47
Other comprehensive income before reclassifications	0	10	13
Amounts reclassified from AOCI	(14)	(16)	(19)
Other comprehensive income (loss)	(14)	(6)	(6)
Income taxes (benefits) on other comprehensive income (loss)	(5)	(2)	(2)
Other comprehensive income (loss), net of tax	(9)	(4)	(4)
AOCI Ending Balance	$ 30	$ 39	$ 43