Supplemental Guarantor Information (Details 1) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
CURRENT ASSETS:
Cash and cash equivalents	$ 67	$ 172	$ 74	$ 202
Receivables-
Customers	1,631	1,614
Other	227	315
Materials and supplies, at average cost	835	861
Derivatives	183	160
Prepayments and other	214	208
Total current assets	3,499	3,768
PROPERTY, PLANT AND EQUIPMENT:
In service	43,748	43,210
Less - Accumulated provision for depreciation	12,823	12,600
Property, plant and equipment in service net of accumulated provision for depreciation	30,925	30,610
Construction work in progress	2,361	2,293
Total net property, plant and equipment	33,286	32,903
INVESTMENTS:
Nuclear plant decommissioning trusts	2,227	2,204
Other	934	936
Total other property and investments	3,215	3,194
DEFERRED CHARGES AND OTHER ASSETS:
Goodwill	6,447	6,447	6,444
Other	1,665	1,719
Total deferred charges and other assets	10,424	10,541
Total assets	50,424	50,406	47,691
CURRENT LIABILITIES:
Currently payable long-term debt	2,296	1,999
Accounts payable-
Accrued taxes	392	543
Derivatives	126	126
Other	946	1,038
Total current liabilities	7,132	7,605
CAPITALIZATION:
Total equity	12,996	13,084
Long-term debt and other long-term obligations	15,814	15,179
Total capitalization	28,814	28,272
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	883	892
Accumulated deferred income taxes	6,542	6,616
Asset retirement obligations	1,767	1,599
Retirement benefits	3,070	3,080
Other	1,751	1,836
Total noncurrent liabilities	14,478	14,529
Total liabilities and capitalization	50,424	50,406
FES
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	489	483
Affiliated companies	434	232
Other	56	56
Notes receivable from affiliated companies	292	366
Materials and supplies, at average cost	62	66
Derivatives	183	158
Prepayments and other	46	38
Total current assets	1,562	1,399
PROPERTY, PLANT AND EQUIPMENT:
In service	114	91
Less - Accumulated provision for depreciation	33	32
Property, plant and equipment in service net of accumulated provision for depreciation	81	59
Construction work in progress	16	34
Total net property, plant and equipment	97	93
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	5,171	4,972
Other	0	0
Total other property and investments	5,171	4,972
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	0	0
Customer intangibles	107	110
Goodwill	24	24
Property taxes	0	0
Unamortized sale and leaseback costs	0	0
Derivatives	87	99
Other	151	160
Total deferred charges and other assets	369	393
Total assets	7,199	6,857
CURRENT LIABILITIES:
Currently payable long-term debt	401	1
Short-term borrowings	0	0
Accounts payable-
Affiliated companies	632	748
Other	104	63
Accrued taxes	31	126
Derivatives	125	124
Other	41	71
Total current liabilities	2,587	1,491
CAPITALIZATION:
Total equity	3,772	3,763
Long-term debt and other long-term obligations	713	1,482
Total capitalization	4,485	5,245
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	18	28
Asset retirement obligations	0	0
Retirement benefits	26	26
Derivatives	53	37
Other	30	30
Total noncurrent liabilities	127	121
Total liabilities and capitalization	7,199	6,857
FES | Affiliates
CURRENT LIABILITIES:
Short-term borrowings	1,253	358
FGCO
CURRENT ASSETS:
Cash and cash equivalents	3	3	7	7
Receivables-
Customers	0	0
Affiliated companies	417	417
Other	25	19
Notes receivable from affiliated companies	0	7
Materials and supplies, at average cost	205	231
Derivatives	0	0
Prepayments and other	50	39
Total current assets	700	716
PROPERTY, PLANT AND EQUIPMENT:
In service	6,193	5,899
Less - Accumulated provision for depreciation	1,933	1,915
Property, plant and equipment in service net of accumulated provision for depreciation	4,260	3,984
Construction work in progress	116	230
Total net property, plant and equipment	4,376	4,214
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	0	0
Other	13	12
Total other property and investments	13	12
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	265	313
Customer intangibles	0	0
Goodwill	0	0
Property taxes	14	14
Unamortized sale and leaseback costs	0	0
Derivatives	0	0
Other	189	194
Total deferred charges and other assets	468	521
Total assets	5,557	5,463
CURRENT LIABILITIES:
Currently payable long-term debt	600	586
Short-term borrowings	4	4
Accounts payable-
Affiliated companies	273	143
Other	95	96
Accrued taxes	19	25
Derivatives	0	0
Other	64	148
Total current liabilities	1,325	1,348
CAPITALIZATION:
Total equity	1,884	1,787
Long-term debt and other long-term obligations	1,887	2,009
Total capitalization	3,771	3,796
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	0	0
Asset retirement obligations	170	29
Retirement benefits	219	215
Derivatives	0	0
Other	72	75
Total noncurrent liabilities	461	319
Total liabilities and capitalization	5,557	5,463
FGCO | Affiliates
CURRENT LIABILITIES:
Short-term borrowings	270	346
Nuclear Generation Corp
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	0	0
Affiliated companies	279	478
Other	64	16
Notes receivable from affiliated companies	1,115	607
Materials and supplies, at average cost	210	208
Derivatives	0	0
Prepayments and other	10	10
Total current assets	1,678	1,319
PROPERTY, PLANT AND EQUIPMENT:
In service	6,412	6,391
Less - Accumulated provision for depreciation	2,727	2,646
Property, plant and equipment in service net of accumulated provision for depreciation	3,685	3,745
Construction work in progress	957	877
Total net property, plant and equipment	4,642	4,622
INVESTMENTS:
Nuclear plant decommissioning trusts	1,306	1,283
Investment in affiliated companies	0	0
Other	0	0
Total other property and investments	1,306	1,283
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	0	0
Customer intangibles	0	0
Goodwill	0	0
Property taxes	22	22
Unamortized sale and leaseback costs	0	0
Derivatives	0	0
Other	4	5
Total deferred charges and other assets	26	27
Total assets	7,652	7,251
CURRENT LIABILITIES:
Currently payable long-term debt	537	537
Short-term borrowings	0	0
Accounts payable-
Affiliated companies	224	583
Other	0	0
Accrued taxes	24	20
Derivatives	0	0
Other	24	15
Total current liabilities	1,395	1,155
CAPITALIZATION:
Total equity	3,266	3,165
Long-term debt and other long-term obligations	834	834
Total capitalization	4,100	3,999
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	744	714
Asset retirement obligations	951	936
Retirement benefits	0	0
Derivatives	0	0
Other	462	447
Total noncurrent liabilities	2,157	2,097
Total liabilities and capitalization	7,652	7,251
Nuclear Generation Corp | Affiliates
CURRENT LIABILITIES:
Short-term borrowings	586	0
Eliminations
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	0	0
Affiliated companies	(634)	(748)
Other	0	0
Notes receivable from affiliated companies	(1,407)	(704)
Materials and supplies, at average cost	0	0
Derivatives	0	0
Prepayments and other	0	0
Total current assets	(2,041)	(1,452)
PROPERTY, PLANT AND EQUIPMENT:
In service	(383)	(384)
Less - Accumulated provision for depreciation	(185)	(185)
Property, plant and equipment in service net of accumulated provision for depreciation	(198)	(199)
Construction work in progress	0	0
Total net property, plant and equipment	(198)	(199)
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	(5,171)	(4,972)
Other	0	0
Total other property and investments	(5,171)	(4,972)
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	(265)	(313)
Customer intangibles	0	0
Goodwill	0	0
Property taxes	0	0
Unamortized sale and leaseback costs	147	119
Derivatives	0	0
Other	(106)	(106)
Total deferred charges and other assets	(224)	(300)
Total assets	(7,634)	(6,923)
CURRENT LIABILITIES:
Currently payable long-term debt	(22)	(22)
Short-term borrowings	0	0
Accounts payable-
Affiliated companies	(634)	(748)
Other	0	0
Accrued taxes	(6)	0
Derivatives	0	0
Other	79	46
Total current liabilities	(1,990)	(1,428)
CAPITALIZATION:
Total equity	(5,150)	(4,952)
Long-term debt and other long-term obligations	(1,208)	(1,207)
Total capitalization	(6,358)	(6,159)
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	883	892
Accumulated deferred income taxes	(171)	(227)
Asset retirement obligations	0	0
Retirement benefits	0	0
Derivatives	0	0
Other	2	(1)
Total noncurrent liabilities	714	664
Total liabilities and capitalization	(7,634)	(6,923)
Eliminations | Affiliates
CURRENT LIABILITIES:
Short-term borrowings	(1,407)	(704)
FES
CURRENT ASSETS:
Cash and cash equivalents	3	3	7	7
Receivables-
Customers	489	483
Affiliated companies	496	379
Other	145	91
Notes receivable from affiliated companies	0	276
Materials and supplies, at average cost	477	505
Derivatives	183	158
Prepayments and other	106	87
Total current assets	1,899	1,982
PROPERTY, PLANT AND EQUIPMENT:
In service	12,336	11,997
Less - Accumulated provision for depreciation	4,508	4,408
Property, plant and equipment in service net of accumulated provision for depreciation	7,828	7,589
Construction work in progress	1,089	1,141
Total net property, plant and equipment	8,917	8,730
INVESTMENTS:
Nuclear plant decommissioning trusts	1,306	1,283
Investment in affiliated companies	0	0
Other	13	12
Total other property and investments	1,319	1,295
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	0	0
Customer intangibles	107	110
Goodwill	24	24
Property taxes	36	36
Unamortized sale and leaseback costs	147	119
Derivatives	87	99
Other	238	253
Total deferred charges and other assets	639	641
Total assets	12,774	12,648
CURRENT LIABILITIES:
Currently payable long-term debt	1,516	1,102
Short-term borrowings	4	4
Accounts payable-
Affiliated companies	495	726
Other	199	159
Accrued taxes	68	171
Derivatives	125	124
Other	208	280
Total current liabilities	3,317	2,566
CAPITALIZATION:
Total equity	3,772	3,763
Long-term debt and other long-term obligations	2,226	3,118
Total capitalization	5,998	6,881
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	883	892
Accumulated deferred income taxes	591	515
Asset retirement obligations	1,121	965
Retirement benefits	245	241
Derivatives	53	37
Other	566	551
Total noncurrent liabilities	3,459	3,201
Total liabilities and capitalization	12,774	12,648
FES | Affiliates
CURRENT LIABILITIES:
Short-term borrowings	$ 702	$ 0