Supplemental Guarantor Information (Details 2) (USD $) In Millions, unless otherwise specified	0 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Feb. 12, 2014	Mar. 31, 2014	Jun. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated Statements of Cash Flows [Abstract]
Net cash provided from operating activities				$ 2,713	$ 2,662	$ 2,320
New Financing-
Long-term debt				4,528	3,745	750
Short-term borrowings, net				0	1,435	1,969
Redemptions and Repayments-
Long-term debt				(1,759)	(3,600)	(940)
Short-term borrowings, net				(1,605)	0	0
Common stock dividend payments				(604)	(920)	(920)
Tender premiums				0	(110)	0
Other				(47)	(73)	(52)
Net cash provided from (used for) financing activities				513	477	807
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions				(3,312)	(2,638)	(2,678)
Nuclear fuel				(233)	(250)	(286)
Proceeds from asset sales	394			394	4	17
Sales of investment securities held in trusts				2,133	2,047	2,980
Purchases of investment securities held in trusts				(2,236)	(2,096)	(3,020)
Other				13	9	(43)
Net cash used for investing activities				(3,359)	(3,093)	(3,157)
Net change in cash and cash equivalents				(133)	46	(30)
Cash and cash equivalents at beginning of period		218	172	218	172	202
Cash and cash equivalents at end of period				85	218	172
FES
Consolidated Statements of Cash Flows [Abstract]
Net cash provided from operating activities				(600)	(1,429)	(1,063)
New Financing-
Long-term debt			0			0
Short-term borrowings, net				247	864	0
Equity contribution from parent				500	1,500
Redemptions and Repayments-
Long-term debt				(1)	(770)	(1)
Short-term borrowings, net				0	(244)	(707)
Common stock dividend payments						0
Tender premiums					(67)
Other				(1)	(4)	(1)
Net cash provided from (used for) financing activities				745	1,279	(709)
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions				(8)	(12)	(14)
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
Loans to affiliated companies, net				(136)	163	(211)
Dividends received						2,000
Other				(1)	(1)	(3)
Net cash used for investing activities				(145)	150	1,772
Net change in cash and cash equivalents				0	0	0
Cash and cash equivalents at beginning of period		0	0	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				408	753	639
New Financing-
Long-term debt			431			351
Short-term borrowings, net				114	371	260
Equity contribution from parent				0	0
Redemptions and Repayments-
Long-term debt				(269)	(364)	(288)
Short-term borrowings, net				0	(505)	0
Common stock dividend payments						(2,000)
Tender premiums					0
Other				(12)	(5)	(8)
Net cash provided from (used for) financing activities				264	(503)	(1,685)
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions				(169)	(256)	(273)
Nuclear fuel				0	0	0
Proceeds from asset sales				307	21	17
Sales of investment securities held in trusts				0	0	0
Purchases of investment securities held in trusts				0	0	0
Loans to affiliated companies, net				(815)	(15)	1,338
Dividends received						0
Other				5	(1)	(40)
Net cash used for investing activities				(672)	(251)	1,042
Net change in cash and cash equivalents				0	(1)	(4)
Cash and cash equivalents at beginning of period		2	3	2	3	7
Cash and cash equivalents at end of period				2	2	3
Nuclear Generation Corp
Consolidated Statements of Cash Flows [Abstract]
Net cash provided from operating activities				785	776	1,266
New Financing-
Long-term debt			447			299
Short-term borrowings, net				0	150	0
Equity contribution from parent				0	0
Redemptions and Repayments-
Long-term debt				(568)	(90)	(161)
Short-term borrowings, net				(123)	0	(32)
Common stock dividend payments						0
Tender premiums					0
Other				(2)	0	(3)
Net cash provided from (used for) financing activities				(246)	60	103
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions				(662)	(449)	(508)
Nuclear fuel				(233)	(250)	(286)
Proceeds from asset sales				0	0	0
Sales of investment securities held in trusts				1,163	940	1,464
Purchases of investment securities held in trusts				(1,219)	(1,000)	(1,502)
Loans to affiliated companies, net				412	(77)	(538)
Dividends received						0
Other				0	0	1
Net cash used for investing activities				(539)	(836)	(1,369)
Net change in cash and cash equivalents				0	0	0
Cash and cash equivalents at beginning of period		0	0	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				(22)	(22)	(21)
New Financing-
Long-term debt			0			0
Short-term borrowings, net				(361)	(954)	(257)
Equity contribution from parent				0	0
Redemptions and Repayments-
Long-term debt				22	22	21
Short-term borrowings, net				(178)	749	739
Common stock dividend payments						2,000
Tender premiums					0
Other					0	0
Net cash provided from (used for) financing activities				(517)	(183)	2,503
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
Loans to affiliated companies, net				539	205	(482)
Dividends received						(2,000)
Other				0	0	0
Net cash used for investing activities				539	205	(2,482)
Net change in cash and cash equivalents				0	0	0
Cash and cash equivalents at beginning of period		0	0	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				571	78	821
New Financing-
Long-term debt			878	878	0	650
Short-term borrowings, net				0	431	3
Equity contribution from parent		500		500	1,500	0
Redemptions and Repayments-
Long-term debt				(816)	(1,202)	(429)
Short-term borrowings, net				(301)	0	0
Common stock dividend payments						0
Tender premiums				0	(67)	0
Other				(15)	(9)	(12)
Net cash provided from (used for) financing activities				246	653	212
CASH FLOWS FROM INVESTING ACTIVITIES:
Property additions				(839)	(717)	(795)
Nuclear fuel				(233)	(250)	(286)
Proceeds from asset sales	307			307	21	17
Sales of investment securities held in trusts				1,163	940	1,464
Purchases of investment securities held in trusts				(1,219)	(1,000)	(1,502)
Loans to affiliated companies, net				0	276	107
Dividends received						0
Other				4	(2)	(42)
Net cash used for investing activities				(817)	(732)	(1,037)
Net change in cash and cash equivalents				0	(1)	(4)
Cash and cash equivalents at beginning of period		2	3	2	3	7
Cash and cash equivalents at end of period				$ 2	$ 2	$ 3