Supplemental Guarantor Information (Details 1) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
CURRENT ASSETS:
Cash and cash equivalents	$ 71	$ 172	$ 94	$ 202
Receivables-
Customers	1,646	1,614
Other	277	315
Materials and supplies, at average cost	806	861
Derivatives	173	160
Prepayments and other	248	208
Total current assets	3,560	3,768
PROPERTY, PLANT AND EQUIPMENT:
In service	43,888	43,210
Less - Accumulated provision for depreciation	13,027	12,600
Property, plant and equipment in service net of accumulated provision for depreciation	30,861	30,610
Construction work in progress	2,230	2,293
Total net property, plant and equipment	33,091	32,903
INVESTMENTS:
Nuclear plant decommissioning trusts	2,178	2,204
Other	876	936
Total other property and investments	3,100	3,194
DEFERRED CHARGES AND OTHER ASSETS:
Goodwill	6,447	6,447	6,444
Other	1,638	1,719
Total deferred charges and other assets	10,406	10,541
Total assets	50,157	50,406	48,048
CURRENT LIABILITIES:
Currently payable long-term debt	1,952	1,999
Accounts payable-
Accrued taxes	338	543
Derivatives	142	126
Other	599	1,038
Total current liabilities	7,533	7,605
CAPITALIZATION:
Total equity	12,799	13,084
Long-term debt and other long-term obligations	15,449	15,179
Total capitalization	28,252	28,272
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	875	892
Accumulated deferred income taxes	6,427	6,616
Asset retirement obligations	1,795	1,599
Retirement benefits	3,088	3,080
Other	1,703	1,836
Total noncurrent liabilities	14,372	14,529
Total liabilities and capitalization	50,157	50,406
FES
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	541	483
Affiliated companies	326	232
Other	86	56
Notes receivable from affiliated companies	573	366
Materials and supplies, at average cost	69	66
Derivatives	170	158
Prepayments and other	83	38
Total current assets	1,848	1,399
PROPERTY, PLANT AND EQUIPMENT:
In service	114	91
Less - Accumulated provision for depreciation	34	32
Property, plant and equipment in service net of accumulated provision for depreciation	80	59
Construction work in progress	19	34
Total net property, plant and equipment	99	93
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	5,334	4,972
Other	0	0
Total other property and investments	5,334	4,972
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	0	0
Customer intangibles	103	110
Goodwill	24	24
Property taxes	0	0
Unamortized sale and leaseback costs	0	0
Derivatives	87	99
Other	144	160
Total deferred charges and other assets	358	393
Total assets	7,639	6,857
CURRENT LIABILITIES:
Currently payable long-term debt	1	1
Short-term borrowings	0	0
Accounts payable-
Affiliated companies	702	748
Other	120	63
Accrued taxes	7	126
Derivatives	140	124
Other	63	71
Total current liabilities	1,632	1,491
CAPITALIZATION:
Total equity	5,193	3,763
Long-term debt and other long-term obligations	712	1,482
Total capitalization	5,905	5,245
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	12	28
Asset retirement obligations	0	0
Retirement benefits	26	26
Derivatives	35	37
Other	29	30
Total noncurrent liabilities	102	121
Total liabilities and capitalization	7,639	6,857
FES | Affiliates
CURRENT LIABILITIES:
Short-term borrowings	599	358
FGCO
CURRENT ASSETS:
Cash and cash equivalents	2	3	7	7
Receivables-
Customers	0	0
Affiliated companies	477	417
Other	30	19
Notes receivable from affiliated companies	14	7
Materials and supplies, at average cost	172	231
Derivatives	0	0
Prepayments and other	39	39
Total current assets	734	716
PROPERTY, PLANT AND EQUIPMENT:
In service	6,234	5,899
Less - Accumulated provision for depreciation	1,964	1,915
Property, plant and equipment in service net of accumulated provision for depreciation	4,270	3,984
Construction work in progress	99	230
Total net property, plant and equipment	4,369	4,214
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	0	0
Other	12	12
Total other property and investments	12	12
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	239	313
Customer intangibles	0	0
Goodwill	0	0
Property taxes	14	14
Unamortized sale and leaseback costs	0	0
Derivatives	0	0
Other	245	194
Total deferred charges and other assets	498	521
Total assets	5,613	5,463
CURRENT LIABILITIES:
Currently payable long-term debt	366	586
Short-term borrowings	4	4
Accounts payable-
Affiliated companies	265	143
Other	136	96
Accrued taxes	14	25
Derivatives	0	0
Other	65	148
Total current liabilities	1,308	1,348
CAPITALIZATION:
Total equity	1,965	1,787
Long-term debt and other long-term obligations	1,875	2,009
Total capitalization	3,840	3,796
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	0	0
Asset retirement obligations	171	29
Retirement benefits	224	215
Derivatives	0	0
Other	70	75
Total noncurrent liabilities	465	319
Total liabilities and capitalization	5,613	5,463
FGCO | Affiliates
CURRENT LIABILITIES:
Short-term borrowings	458	346
Nuclear Generation Corp
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	0	0
Affiliated companies	325	478
Other	6	16
Notes receivable from affiliated companies	590	607
Materials and supplies, at average cost	213	208
Derivatives	0	0
Prepayments and other	7	10
Total current assets	1,141	1,319
PROPERTY, PLANT AND EQUIPMENT:
In service	6,598	6,391
Less - Accumulated provision for depreciation	2,798	2,646
Property, plant and equipment in service net of accumulated provision for depreciation	3,800	3,745
Construction work in progress	898	877
Total net property, plant and equipment	4,698	4,622
INVESTMENTS:
Nuclear plant decommissioning trusts	1,270	1,283
Investment in affiliated companies	0	0
Other	0	0
Total other property and investments	1,270	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	13	5
Total deferred charges and other assets	35	27
Total assets	7,144	7,251
CURRENT LIABILITIES:
Currently payable long-term debt	514	537
Short-term borrowings	0	0
Accounts payable-
Affiliated companies	252	583
Other	0	0
Accrued taxes	20	20
Derivatives	0	0
Other	16	15
Total current liabilities	802	1,155
CAPITALIZATION:
Total equity	3,347	3,165
Long-term debt and other long-term obligations	789	834
Total capitalization	4,136	3,999
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	770	714
Asset retirement obligations	967	936
Retirement benefits	0	0
Derivatives	0	0
Other	469	447
Total noncurrent liabilities	2,206	2,097
Total liabilities and capitalization	7,144	7,251
Nuclear Generation Corp | Affiliates
CURRENT LIABILITIES:
Short-term borrowings	0	0
Eliminations
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	0	0
Affiliated companies	(693)	(748)
Other	0	0
Notes receivable from affiliated companies	(1,057)	(704)
Materials and supplies, at average cost	0	0
Derivatives	0	0
Prepayments and other	0	0
Total current assets	(1,750)	(1,452)
PROPERTY, PLANT AND EQUIPMENT:
In service	(383)	(384)
Less - Accumulated provision for depreciation	(186)	(185)
Property, plant and equipment in service net of accumulated provision for depreciation	(197)	(199)
Construction work in progress	0	0
Total net property, plant and equipment	(197)	(199)
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	(5,334)	(4,972)
Other	0	0
Total other property and investments	(5,334)	(4,972)
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	(239)	(313)
Customer intangibles	0	0
Goodwill	0	0
Property taxes	0	0
Unamortized sale and leaseback costs	164	119
Derivatives	0	0
Other	(163)	(106)
Total deferred charges and other assets	(238)	(300)
Total assets	(7,519)	(6,923)
CURRENT LIABILITIES:
Currently payable long-term debt	(22)	(22)
Short-term borrowings	0	0
Accounts payable-
Affiliated companies	(705)	(748)
Other	0	0
Accrued taxes	(1)	0
Derivatives	0	0
Other	35	46
Total current liabilities	(1,750)	(1,428)
CAPITALIZATION:
Total equity	(5,312)	(4,952)
Long-term debt and other long-term obligations	(1,196)	(1,207)
Total capitalization	(6,508)	(6,159)
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	875	892
Accumulated deferred income taxes	(135)	(227)
Asset retirement obligations	0	0
Retirement benefits	0	0
Derivatives	0	0
Other	(1)	(1)
Total noncurrent liabilities	739	664
Total liabilities and capitalization	(7,519)	(6,923)
Eliminations | Affiliates
CURRENT LIABILITIES:
Short-term borrowings	(1,057)	(704)
FES
CURRENT ASSETS:
Cash and cash equivalents	2	3	7	7
Receivables-
Customers	541	483
Affiliated companies	435	379
Other	122	91
Notes receivable from affiliated companies	120	276
Materials and supplies, at average cost	454	505
Derivatives	170	158
Prepayments and other	129	87
Total current assets	1,973	1,982
PROPERTY, PLANT AND EQUIPMENT:
In service	12,563	11,997
Less - Accumulated provision for depreciation	4,610	4,408
Property, plant and equipment in service net of accumulated provision for depreciation	7,953	7,589
Construction work in progress	1,016	1,141
Total net property, plant and equipment	8,969	8,730
INVESTMENTS:
Nuclear plant decommissioning trusts	1,270	1,283
Investment in affiliated companies	0	0
Other	12	12
Total other property and investments	1,282	1,295
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	0	0
Customer intangibles	103	110
Goodwill	24	24
Property taxes	36	36
Unamortized sale and leaseback costs	164	119
Derivatives	87	99
Other	239	253
Total deferred charges and other assets	653	641
Total assets	12,877	12,648
CURRENT LIABILITIES:
Currently payable long-term debt	859	1,102
Short-term borrowings	4	4
Accounts payable-
Affiliated companies	514	726
Other	256	159
Accrued taxes	40	171
Derivatives	140	124
Other	179	280
Total current liabilities	1,992	2,566
CAPITALIZATION:
Total equity	5,193	3,763
Long-term debt and other long-term obligations	2,180	3,118
Total capitalization	7,373	6,881
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	875	892
Accumulated deferred income taxes	647	515
Asset retirement obligations	1,138	965
Retirement benefits	250	241
Derivatives	35	37
Other	567	551
Total noncurrent liabilities	3,512	3,201
Total liabilities and capitalization	12,877	12,648
FES | Affiliates
CURRENT LIABILITIES:
Short-term borrowings	$ 0	$ 0