Supplemental Guarantor Information (Details 2) - USD ($) $ in Millions		12 Months Ended
	Feb. 12, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Consolidated Statements of Cash Flows [Abstract]
Net cash provided from operating activities		$ 3,447	$ 2,713	$ 2,662
New Financing-
Long-term debt		1,311	4,528	3,745
Short-term borrowings, net		0	0	1,435
Redemptions and Repayments-
Long-term debt		(879)	(1,759)	(3,600)
Short-term borrowings, net		(91)	(1,605)	0
Common stock dividend payments		(607)	(604)	(920)
Tender premiums		0	0	(110)
Other		(13)	(47)	(73)
Net cash provided from (used for) financing activities		(279)	513	477
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions		(2,704)	(3,312)	(2,638)
Nuclear fuel		(190)	(233)	(250)
Proceeds from asset sales	$ 394	20	394	4
Sales of investment securities held in trusts		1,534	2,133	2,047
Purchases of investment securities held in trusts		(1,648)	(2,236)	(2,096)
Cash investments		7	35	(23)
Other		1	13	9
Net cash used for investing activities		(3,122)	(3,359)	(3,093)
Net change in cash and cash equivalents		46	(133)	46
Cash and cash equivalents at beginning of period		85	218	172
Cash and cash equivalents at end of period		131	85	218
FES
Consolidated Statements of Cash Flows [Abstract]
Net cash provided from operating activities		(637)	(600)	(1,429)
New Financing-
Long-term debt		0	0
Short-term borrowings, net		796	247	864
Equity contribution from parent			500	1,500
Redemptions and Repayments-
Long-term debt		(17)	(1)	(770)
Short-term borrowings, net		0	0	(244)
Common stock dividend payments		(70)
Tender premiums				(67)
Other			(1)	(4)
Net cash provided from (used for) financing activities		709	745	1,279
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions		(5)	(8)	(12)
Nuclear fuel		0	0	0
Proceeds from asset sales		10	0	0
Sales of investment securities held in trusts		0	0	0
Purchases of investment securities held in trusts		0	0	0
Cash investments		(10)
Loans to affiliated companies, net		(67)	(136)	163
Other		0	(1)	(1)
Net cash used for investing activities		(72)	(145)	150
Net change in cash and cash equivalents		0	0	0
Cash and cash equivalents at beginning of period		0	0	0
Cash and cash equivalents at end of period		0	0	0
FGCO
Consolidated Statements of Cash Flows [Abstract]
Net cash provided from operating activities		551	408	753
New Financing-
Long-term debt		45	431
Short-term borrowings, net		67	114	371
Equity contribution from parent			0	0
Redemptions and Repayments-
Long-term debt		(70)	(269)	(364)
Short-term borrowings, net		0	0	(505)
Common stock dividend payments		0
Tender premiums				0
Other		(5)	(12)	(5)
Net cash provided from (used for) financing activities		37	264	(503)
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions		(223)	(169)	(256)
Nuclear fuel		0	0	0
Proceeds from asset sales		3	307	21
Sales of investment securities held in trusts		0	0	0
Purchases of investment securities held in trusts		0	0	0
Cash investments		0
Loans to affiliated companies, net		(372)	(815)	(15)
Other		4	5	(1)
Net cash used for investing activities		(588)	(672)	(251)
Net change in cash and cash equivalents		0	0	(1)
Cash and cash equivalents at beginning of period		2	2	3
Cash and cash equivalents at end of period		2	2	2
Nuclear Generation Corp
Consolidated Statements of Cash Flows [Abstract]
Net cash provided from operating activities		1,261	785	776
New Financing-
Long-term debt		296	447
Short-term borrowings, net		0	0	150
Equity contribution from parent			0	0
Redemptions and Repayments-
Long-term debt		(348)	(568)	(90)
Short-term borrowings, net		(28)	(123)	0
Common stock dividend payments		0
Tender premiums				0
Other		(1)	(2)	0
Net cash provided from (used for) financing activities		(81)	(246)	60
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions		(399)	(662)	(449)
Nuclear fuel		(190)	(233)	(250)
Proceeds from asset sales		0	0	0
Sales of investment securities held in trusts		733	1,163	940
Purchases of investment securities held in trusts		(791)	(1,219)	(1,000)
Cash investments		0
Loans to affiliated companies, net		(533)	412	(77)
Other		0	0	0
Net cash used for investing activities		(1,180)	(539)	(836)
Net change in cash and cash equivalents		0	0	0
Cash and cash equivalents at beginning of period		0	0	0
Cash and cash equivalents at end of period		0	0	0
Eliminations
Consolidated Statements of Cash Flows [Abstract]
Net cash provided from operating activities		(24)	(22)	(22)
New Financing-
Long-term debt		0	0
Short-term borrowings, net		(863)	(361)	(954)
Equity contribution from parent			0	0
Redemptions and Repayments-
Long-term debt		24	22	22
Short-term borrowings, net		(98)	(178)	749
Common stock dividend payments		0
Tender premiums				0
Other			0	0
Net cash provided from (used for) financing activities		(937)	(517)	(183)
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions		0	0	0
Nuclear fuel		0	0	0
Proceeds from asset sales		0	0	0
Sales of investment securities held in trusts		0	0	0
Purchases of investment securities held in trusts		0	0	0
Cash investments		0
Loans to affiliated companies, net		961	539	205
Other		0	0	0
Net cash used for investing activities		961	539	205
Net change in cash and cash equivalents		0	0	0
Cash and cash equivalents at beginning of period		0	0	0
Cash and cash equivalents at end of period		0	0	0
FES
Consolidated Statements of Cash Flows [Abstract]
Net cash provided from operating activities		1,151	571	78
New Financing-
Long-term debt		341	878	0
Short-term borrowings, net		0	0	431
Equity contribution from parent		0	500	1,500
Redemptions and Repayments-
Long-term debt		(411)	(816)	(1,202)
Short-term borrowings, net		(126)	(301)	0
Common stock dividend payments		(70)	0	0
Tender premiums		0	0	(67)
Other		(6)	(15)	(9)
Net cash provided from (used for) financing activities		(272)	246	653
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions		(627)	(839)	(717)
Nuclear fuel		(190)	(233)	(250)
Proceeds from asset sales	$ 307	13	307	21
Sales of investment securities held in trusts		733	1,163	940
Purchases of investment securities held in trusts		(791)	(1,219)	(1,000)
Cash investments		(10)	0	0
Loans to affiliated companies, net		(11)	0	276
Other		4	4	(2)
Net cash used for investing activities		(879)	(817)	(732)
Net change in cash and cash equivalents		0	0	(1)
Cash and cash equivalents at beginning of period		2	2	3
Cash and cash equivalents at end of period		$ 2	$ 2	$ 2