Supplemental Guarantor Information (Details 1) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
CURRENT ASSETS:
Cash and cash equivalents	$ 114	$ 199	$ 199	$ 131
Receivables-
Customers	1,375	1,440
Other	161	175
Materials and supplies	553	564
Derivatives	45	140
Collateral	129	176
Prepaid taxes and other	151	158
Total current assets	2,755	2,950
PROPERTY, PLANT AND EQUIPMENT:
In service	43,929	43,767
Less — Accumulated provision for depreciation	15,999	15,731
Property, plant and equipment in service net of accumulated provision for depreciation	27,930	28,036
Construction work in progress	1,249	1,351
Total net property, plant and equipment	29,179	29,387
INVESTMENTS:
Nuclear plant decommissioning trusts	2,588	2,514
Other	507	512
Total other property and investments	3,095	3,026
DEFERRED CHARGES AND OTHER ASSETS:
Other	871	1,153
Total deferred charges and other assets	7,483	7,785
Total assets	43,327	43,148	51,401
CURRENT LIABILITIES:
Currently payable long-term debt	2,015	1,685
Accounts payable-
Accrued taxes	518	580
Derivatives	18	78
Other	619	660
Total current liabilities	4,647	7,126
CAPITALIZATION:
Total equity	6,320	6,241
Long-term debt and other long-term obligations	20,582	18,192
Total capitalization	26,902	24,433
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	740	757
Accumulated deferred income taxes	3,992	3,765
Retirement benefits	3,784	3,719
Asset retirement obligations	1,526	1,482
Other	1,584	1,704
Total noncurrent liabilities	11,778	11,589
Total liabilities and capitalization	43,327	43,148
Eliminations
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	0	0
Affiliated companies	(392)	(612)
Other	0	0
Notes receivable from affiliated companies	(3,326)	(3,351)
Materials and supplies	0	0
Derivatives	0	0
Collateral	0	0
Prepaid taxes and other	0	0
Total current assets	(3,718)	(3,963)
PROPERTY, PLANT AND EQUIPMENT:
In service	(281)	(290)
Less — Accumulated provision for depreciation	(188)	(187)
Property, plant and equipment in service net of accumulated provision for depreciation	(93)	(103)
Construction work in progress	0	0
Total net property, plant and equipment	(93)	(103)
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	(3,230)	(2,923)
Other	0	0
Total other property and investments	(3,230)	(2,923)
DEFERRED CHARGES AND OTHER ASSETS:
Property taxes	0	0
Accumulated deferred income tax benefits	(273)	(270)
Derivatives	0	0
Other	18	21
Total deferred charges and other assets	(255)	(249)
Total assets	(7,296)	(7,238)
CURRENT LIABILITIES:
Currently payable long-term debt	(27)	(26)
Accounts payable-
Affiliated companies	(473)	(706)
Other	0	0
Accrued taxes	(29)	(16)
Derivatives	0	0
Other	33	36
Total current liabilities	(3,822)	(4,063)
CAPITALIZATION:
Total equity	(3,131)	(2,834)
Long-term debt and other long-term obligations	(1,078)	(1,091)
Total capitalization	(4,209)	(3,925)
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	740	757
Accumulated deferred income taxes	(5)	(7)
Retirement benefits	0	0
Asset retirement obligations	0	0
Derivatives	0	0
Other	0	0
Total noncurrent liabilities	735	750
Total liabilities and capitalization	(7,296)	(7,238)
Eliminations | Affiliates
CURRENT LIABILITIES:
Short-term borrowings - affiliated companies	(3,326)	(3,351)
FES
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	185	213
Affiliated companies	300	332
Other	10	17
Notes receivable from affiliated companies	361	501
Materials and supplies	41	45
Derivatives	41	137
Collateral	98	157
Prepaid taxes and other	40	38
Total current assets	1,076	1,440
PROPERTY, PLANT AND EQUIPMENT:
In service	121	120
Less — Accumulated provision for depreciation	59	52
Property, plant and equipment in service net of accumulated provision for depreciation	62	68
Construction work in progress	2	2
Total net property, plant and equipment	64	70
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	3,230	2,923
Other	0	0
Total other property and investments	3,230	2,923
DEFERRED CHARGES AND OTHER ASSETS:
Property taxes	0	0
Accumulated deferred income tax benefits	440	395
Derivatives	9	77
Other	32	33
Total deferred charges and other assets	481	505
Total assets	4,851	4,938
CURRENT LIABILITIES:
Currently payable long-term debt	0	0
Accounts payable-
Affiliated companies	477	743
Other	17	17
Accrued taxes	48	50
Derivatives	15	71
Other	47	56
Total current liabilities	3,845	3,906
CAPITALIZATION:
Total equity	239	218
Long-term debt and other long-term obligations	691	691
Total capitalization	930	909
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	5	4
Retirement benefits	27	25
Asset retirement obligations	0	0
Derivatives	1	52
Other	43	42
Total noncurrent liabilities	76	123
Total liabilities and capitalization	4,851	4,938
FES | Affiliates
CURRENT LIABILITIES:
Short-term borrowings - affiliated companies	3,241	2,969
FG
CURRENT ASSETS:
Cash and cash equivalents	2	2	2	2
Receivables-
Customers	0	0
Affiliated companies	240	315
Other	2	2
Notes receivable from affiliated companies	1,599	1,585
Materials and supplies	137	142
Derivatives	0	0
Collateral	13	0
Prepaid taxes and other	11	24
Total current assets	2,004	2,070
PROPERTY, PLANT AND EQUIPMENT:
In service	2,561	2,524
Less — Accumulated provision for depreciation	1,936	1,920
Property, plant and equipment in service net of accumulated provision for depreciation	625	604
Construction work in progress	55	67
Total net property, plant and equipment	680	671
INVESTMENTS:
Nuclear plant decommissioning trusts	0	0
Investment in affiliated companies	0	0
Other	9	9
Total other property and investments	9	9
DEFERRED CHARGES AND OTHER ASSETS:
Property taxes	6	12
Accumulated deferred income tax benefits	1,203	1,271
Derivatives	0	0
Other	329	327
Total deferred charges and other assets	1,538	1,610
Total assets	4,231	4,360
CURRENT LIABILITIES:
Currently payable long-term debt	183	200
Accounts payable-
Affiliated companies	92	107
Other	74	93
Accrued taxes	51	48
Derivatives	3	6
Other	80	54
Total current liabilities	843	991
CAPITALIZATION:
Total equity	914	828
Long-term debt and other long-term obligations	1,938	2,093
Total capitalization	2,852	2,921
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	0	3
Retirement benefits	178	172
Asset retirement obligations	188	188
Derivatives	0	0
Other	170	85
Total noncurrent liabilities	536	448
Total liabilities and capitalization	4,231	4,360
FG | Affiliates
CURRENT LIABILITIES:
Short-term borrowings - affiliated companies	360	483
NG
CURRENT ASSETS:
Cash and cash equivalents	0	0	0	0
Receivables-
Customers	0	0
Affiliated companies	237	417
Other	0	8
Notes receivable from affiliated companies	1,366	1,294
Materials and supplies	82	80
Derivatives	0	0
Collateral	0	0
Prepaid taxes and other	0	1
Total current assets	1,685	1,800
PROPERTY, PLANT AND EQUIPMENT:
In service	4,981	4,703
Less — Accumulated provision for depreciation	4,248	4,144
Property, plant and equipment in service net of accumulated provision for depreciation	733	559
Construction work in progress	242	358
Total net property, plant and equipment	975	917
INVESTMENTS:
Nuclear plant decommissioning trusts	1,793	1,552
Investment in affiliated companies	0	0
Other	0	1
Total other property and investments	1,793	1,553
DEFERRED CHARGES AND OTHER ASSETS:
Property taxes	14	28
Accumulated deferred income tax benefits	738	883
Derivatives	0	0
Other	0	0
Total deferred charges and other assets	752	911
Total assets	5,205	5,181
CURRENT LIABILITIES:
Currently payable long-term debt	99	5
Accounts payable-
Affiliated companies	168	406
Other	0	0
Accrued taxes	59	61
Derivatives	0	0
Other	10	10
Total current liabilities	336	482
CAPITALIZATION:
Total equity	2,217	2,006
Long-term debt and other long-term obligations	1,022	1,120
Total capitalization	3,239	3,126
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	0	0
Accumulated deferred income taxes	0	0
Retirement benefits	0	0
Asset retirement obligations	787	713
Derivatives	0	0
Other	843	860
Total noncurrent liabilities	1,630	1,573
Total liabilities and capitalization	5,205	5,181
NG | Affiliates
CURRENT LIABILITIES:
Short-term borrowings - affiliated companies	0	0
Consolidated
CURRENT ASSETS:
Cash and cash equivalents	2	2	$ 2	$ 2
Receivables-
Customers	185	213
Affiliated companies	385	452
Other	12	27
Notes receivable from affiliated companies	0	29
Materials and supplies	260	267
Derivatives	41	137
Collateral	111	157
Prepaid taxes and other	51	63
Total current assets	1,047	1,347
PROPERTY, PLANT AND EQUIPMENT:
In service	7,382	7,057
Less — Accumulated provision for depreciation	6,055	5,929
Property, plant and equipment in service net of accumulated provision for depreciation	1,327	1,128
Construction work in progress	299	427
Total net property, plant and equipment	1,626	1,555
INVESTMENTS:
Nuclear plant decommissioning trusts	1,793	1,552
Investment in affiliated companies	0	0
Other	9	10
Total other property and investments	1,802	1,562
DEFERRED CHARGES AND OTHER ASSETS:
Property taxes	20	40
Accumulated deferred income tax benefits	2,108	2,279
Derivatives	9	77
Other	379	381
Total deferred charges and other assets	2,516	2,777
Total assets	6,991	7,241
CURRENT LIABILITIES:
Currently payable long-term debt	255	179
Accounts payable-
Affiliated companies	264	550
Other	91	110
Accrued taxes	129	143
Derivatives	18	77
Other	170	156
Total current liabilities	1,202	1,316
CAPITALIZATION:
Total equity	239	218
Long-term debt and other long-term obligations	2,573	2,813
Total capitalization	2,812	3,031
NONCURRENT LIABILITIES:
Deferred gain on sale and leaseback transaction	740	757
Accumulated deferred income taxes	0	0
Retirement benefits	205	197
Asset retirement obligations	975	901
Derivatives	1	52
Other	1,056	987
Total noncurrent liabilities	2,977	2,894
Total liabilities and capitalization	6,991	7,241
Consolidated | Affiliates
CURRENT LIABILITIES:
Short-term borrowings - affiliated companies	$ 275	$ 101