Supplemental Guarantor Information (Details 1) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CURRENT ASSETS:
Cash and cash equivalents	$ 131	$ 85	$ 218	$ 172
Receivables-
Customers	1,415	1,554
Other Receivables	180	225
Materials and supplies, at average cost	785	817
Derivatives	157	159
Collateral	70	230
Prepayments and other	167	160
Total current assets	3,040	3,358
PROPERTY, PLANT AND EQUIPMENT:
In service	49,952	47,484
Less - Accumulated provision for depreciation	15,160	14,150
Property, plant and equipment in service net of accumulated provision for depreciation	34,792	33,334
Construction work in progress	2,422	2,449
Total net property, plant and equipment	37,214	35,783
INVESTMENTS:
Nuclear plant decommissioning trusts	2,282	2,341
Other	506	881
Total other property and investments	2,788	3,222
DEFERRED CHARGES AND OTHER ASSETS:
Customer intangibles	331
Goodwill	6,418	6,418	6,418
Other	1,379	1,456
Total deferred charges and other assets	9,145	9,285
Total assets	52,187	51,648	50,424
CURRENT LIABILITIES:
Currently payable long-term debt	1,166	804
Short-term borrowings	1,708	1,799
Accounts payable-
Accrued taxes	519	490
Derivatives	106	167
Other	694	693
Total current liabilities	5,602	5,561
CAPITALIZATION:
Total equity	12,421	12,420
Long-term debt and other long-term obligations	19,192	19,176
Total capitalization	31,614	31,598
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	791	824
Accumulated deferred income taxes	6,773	6,539
Asset retirement obligations	1,410	1,387
Retirement benefits	4,245	3,932
Other	1,555	1,590
Total noncurrent liabilities	14,971	14,489
Total liabilities and capitalization	52,187	51,648
FES
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	275	415
Affiliated companies	433	484
Other Receivables	36	66
Notes receivable from affiliated companies	406	339
Materials and supplies, at average cost	53	67
Derivatives	154	147
Collateral	70	229
Prepayments and other	48	48
Total current assets	1,475	1,795
PROPERTY, PLANT AND EQUIPMENT:
In service	93	133
Less - Accumulated provision for depreciation	40	36
Property, plant and equipment in service net of accumulated provision for depreciation	53	97
Construction work in progress	30	3
Total net property, plant and equipment	83	100
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	7,452	6,607
Other	0	0
Total other property and investments	7,452	6,607
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	300	284
Customer intangibles	61	78
Goodwill	23	23
Property taxes	0	0
Unamortized sale and leaseback costs		0
Derivatives	79	52
Other	33	34
Total deferred charges and other assets	496	471
Total assets	9,506	8,973
CURRENT LIABILITIES:
Currently payable long-term debt	0	18
Short-term borrowings	0	90
Accounts payable-
Affiliated companies	884	1,068
Other	21	46
Accrued taxes	7	2
Derivatives	103	166
Other	66	72
Total current liabilities	3,102	2,597
CAPITALIZATION:
Total equity	5,605	5,585
Long-term debt and other long-term obligations	694	695
Total capitalization	6,299	6,280
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	6	13
Asset retirement obligations	0	0
Retirement benefits	27	36
Derivatives	37	14
Other	35	33
Total noncurrent liabilities	105	96
Total liabilities and capitalization	9,506	8,973
FES | Affiliates
CURRENT LIABILITIES:
Other Short-term Borrowings	2,021	1,135
FGCO
CURRENT ASSETS:
Cash and cash equivalents	2	2	2	3
Receivables-
Customers	0	0
Affiliated companies	403	487
Other Receivables	4	21
Notes receivable from affiliated companies	1,210	838
Materials and supplies, at average cost	204	202
Derivatives	0	0
Collateral	0	0
Prepayments and other	18	19
Total current assets	1,841	1,569
PROPERTY, PLANT AND EQUIPMENT:
In service	6,367	6,217
Less - Accumulated provision for depreciation	2,144	2,058
Property, plant and equipment in service net of accumulated provision for depreciation	4,223	4,159
Construction work in progress	249	206
Total net property, plant and equipment	4,472	4,365
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	0	0
Other	10	10
Total other property and investments	10	10
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	16	98
Customer intangibles	0	0
Goodwill	0	0
Property taxes	12	14
Unamortized sale and leaseback costs		0
Derivatives	0	0
Other	318	277
Total deferred charges and other assets	346	389
Total assets	6,669	6,333
CURRENT LIABILITIES:
Currently payable long-term debt	229	164
Short-term borrowings	8	9
Accounts payable-
Affiliated companies	146	197
Other	118	202
Accrued taxes	93	62
Derivatives	1	0
Other	61	56
Total current liabilities	1,045	1,011
CAPITALIZATION:
Total equity	2,944	2,561
Long-term debt and other long-term obligations	2,122	2,215
Total capitalization	5,066	4,776
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	0	0
Asset retirement obligations	191	189
Retirement benefits	305	288
Derivatives	1	0
Other	61	69
Total noncurrent liabilities	558	546
Total liabilities and capitalization	6,669	6,333
FGCO | Affiliates
CURRENT LIABILITIES:
Other Short-term Borrowings	389	321
Nuclear Generation Corp
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	0	0
Affiliated companies	461	674
Other Receivables	19	20
Notes receivable from affiliated companies	805	272
Materials and supplies, at average cost	213	223
Derivatives	0	0
Collateral	0	0
Prepayments and other	0	0
Total current assets	1,498	1,189
PROPERTY, PLANT AND EQUIPMENT:
In service	8,233	7,628
Less - Accumulated provision for depreciation	3,775	3,305
Property, plant and equipment in service net of accumulated provision for depreciation	4,458	4,323
Construction work in progress	878	801
Total net property, plant and equipment	5,336	5,124
INVESTMENTS:
Nuclear plant decommissioning trusts	1,327	1,365
Investment in affiliated companies	0	0
Other	0	0
Total other property and investments	1,327	1,365
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	0	0
Customer intangibles	0	0
Goodwill	0	0
Property taxes	28	27
Unamortized sale and leaseback costs		0
Derivatives	0	0
Other	21	7
Total deferred charges and other assets	49	34
Total assets	8,210	7,712
CURRENT LIABILITIES:
Currently payable long-term debt	308	348
Short-term borrowings	0	0
Accounts payable-
Affiliated companies	368	219
Other	0	0
Accrued taxes	62	161
Derivatives	0	0
Other	9	9
Total current liabilities	747	765
CAPITALIZATION:
Total equity	4,476	4,014
Long-term debt and other long-term obligations	847	859
Total capitalization	5,323	4,873
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	697	678
Asset retirement obligations	640	652
Retirement benefits	0	0
Derivatives	0	0
Other	803	744
Total noncurrent liabilities	2,140	2,074
Total liabilities and capitalization	8,210	7,712
Nuclear Generation Corp | Affiliates
CURRENT LIABILITIES:
Other Short-term Borrowings	0	28
Eliminations
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	0	0
Affiliated companies	(846)	(1,120)
Other Receivables	0	0
Notes receivable from affiliated companies	(2,410)	(1,449)
Materials and supplies, at average cost	0	0
Derivatives	0	0
Collateral	0	0
Prepayments and other	0	1
Total current assets	(3,256)	(2,568)
PROPERTY, PLANT AND EQUIPMENT:
In service	(382)	(382)
Less - Accumulated provision for depreciation	(194)	(191)
Property, plant and equipment in service net of accumulated provision for depreciation	(188)	(191)
Construction work in progress	0	0
Total net property, plant and equipment	(188)	(191)
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	(7,452)	(6,607)
Other	0	0
Total other property and investments	(7,452)	(6,607)
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	(316)	(382)
Customer intangibles	0	0
Goodwill	0	0
Property taxes	0	0
Unamortized sale and leaseback costs		0
Derivatives	0	0
Other	12	13
Total deferred charges and other assets	(304)	(369)
Total assets	(11,200)	(9,735)
CURRENT LIABILITIES:
Currently payable long-term debt	(25)	(24)
Short-term borrowings	0	0
Accounts payable-
Affiliated companies	(856)	(1,068)
Other	0	0
Accrued taxes	(86)	(123)
Derivatives	0	0
Other	45	47
Total current liabilities	(3,332)	(2,617)
CAPITALIZATION:
Total equity	(7,420)	(6,575)
Long-term debt and other long-term obligations	(1,136)	(1,161)
Total capitalization	(8,556)	(7,736)
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	791	824
Accumulated deferred income taxes	(103)	(207)
Asset retirement obligations	0	0
Retirement benefits	0	0
Derivatives	0	0
Other	0	1
Total noncurrent liabilities	688	618
Total liabilities and capitalization	(11,200)	(9,735)
Eliminations | Affiliates
CURRENT LIABILITIES:
Other Short-term Borrowings	(2,410)	(1,449)
FES
CURRENT ASSETS:
Cash and cash equivalents	2	2	$ 2	$ 3
Receivables-
Customers	275	415
Affiliated companies	451	525
Other Receivables	59	107
Notes receivable from affiliated companies	11	0
Materials and supplies, at average cost	470	492
Derivatives	154	147
Collateral	70	229
Prepayments and other	66	68
Total current assets	1,558	1,985
PROPERTY, PLANT AND EQUIPMENT:
In service	14,311	13,596
Less - Accumulated provision for depreciation	5,765	5,208
Property, plant and equipment in service net of accumulated provision for depreciation	8,546	8,388
Construction work in progress	1,157	1,010
Total net property, plant and equipment	9,703	9,398
INVESTMENTS:
Nuclear plant decommissioning trusts	1,327	1,365
Investment in affiliated companies	0	0
Other	10	10
Total other property and investments	1,337	1,375
DEFERRED CHARGES AND OTHER ASSETS:
Accumulated deferred income tax benefits	0	0
Customer intangibles	61	78
Goodwill	23	23
Property taxes	40	41
Unamortized sale and leaseback costs		0
Derivatives	79	52
Other	384	331
Total deferred charges and other assets	587	525
Total assets	13,185	13,283
CURRENT LIABILITIES:
Currently payable long-term debt	512	506
Short-term borrowings	8	99
Accounts payable-
Affiliated companies	542	416
Other	139	248
Accrued taxes	76	102
Derivatives	104	166
Other	181	184
Total current liabilities	1,562	1,756
CAPITALIZATION:
Total equity	5,605	5,585
Long-term debt and other long-term obligations	2,527	2,608
Total capitalization	8,132	8,193
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	791	824
Accumulated deferred income taxes	600	484
Asset retirement obligations	831	841
Retirement benefits	332	324
Derivatives	38	14
Other	899	847
Total noncurrent liabilities	3,491	3,334
Total liabilities and capitalization	13,185	13,283
FES | Affiliates
CURRENT LIABILITIES:
Other Short-term Borrowings	$ 0	$ 35