Commitments, Guarantees and Contingencies (Details Textuals) (USD $)	12 Months Ended			21 Months Ended	12 Months Ended		12 Months Ended	1 Months Ended	12 Months Ended			12 Months Ended						12 Months Ended		12 Months Ended			12 Months Ended								12 Months Ended	3 Months Ended			3 Months Ended	12 Months Ended			12 Months Ended			16 Months Ended	0 Months Ended	12 Months Ended									12 Months Ended		0 Months Ended	12 Months Ended				3 Months Ended			12 Months Ended
	Dec. 31, 2012 NuclearPowerPlants	Dec. 31, 2011	Dec. 31, 2010	Dec. 05, 2011 allegation aspect_of_opinion	Dec. 31, 2012 Clean Water Act	Apr. 30, 2009 Clean Water Act aspect_of_opinion	Dec. 31, 2012 Regulation of Waste Disposal options	Dec. 31, 2012 Nuclear Plant Matters	Dec. 31, 2012 Nuclear Plant Matters	Dec. 28, 2012 Nuclear Plant Matters decision	Feb. 16, 2012 Nuclear Plant Matters NuclearPowerPlants	Dec. 31, 2012 Caa Compliance CoalFiredPlants ElectricGenerationUnits	Dec. 31, 2012 National Ambient Air Quality Standards T	Dec. 31, 2012 National Ambient Air Quality Standards CAIR phases	Dec. 31, 2012 National Ambient Air Quality Standards CSAPR phases	Dec. 31, 2012 Hazardous Air Pollutant Emissions	Feb. 08, 2012 Hazardous Air Pollutant Emissions CoalFiredPlants	Dec. 31, 2012 Climate Change celsius	Jan. 02, 2011 Climate Change T	Dec. 31, 2012 Climate Change Year 2020 Increase in funding	Dec. 31, 2012 Senior Secured Term Loan Senior Loans	Dec. 31, 2012 Regulated Distribution	Dec. 31, 2012 OE	Dec. 31, 2011 OE	Dec. 31, 2010 OE	Dec. 31, 2012 FES	Dec. 31, 2011 FES	Dec. 31, 2010 FES	Dec. 31, 2012 FES Hazardous Air Pollutant Emissions	Dec. 31, 2012 AE Supply	Dec. 31, 2012 AE Supply ICG Litigation	Dec. 31, 2012 Global Holding	Dec. 31, 2012 Global Holding Senior Secured Term Loan Senior Loans	Dec. 31, 2012 Global Holding Senior Secured Term Loan Senior Loans Signal Peak, Global Rail and Affiliates	Dec. 31, 2012 Signal Peak and Global Rail	Dec. 31, 2012 Signal Peak and Global Rail Senior Secured Term Loan Senior Loans	Dec. 31, 2012 FEV Senior Secured Term Loan Senior Loans Signal Peak Global Holding	Dec. 31, 2012 WMB Marketing Ventures, LLC Senior Secured Term Loan Senior Loans Signal Peak Global Holding	Dec. 31, 2012 FGCO	Dec. 31, 2011 FGCO	Dec. 31, 2010 FGCO	Feb. 27, 2007 FGCO Clean Water Act spills	Jan. 10, 2013 FGCO Clean Water Act Subsequent Event acre	Dec. 31, 2012 FGCO Caa Compliance Complaints	Dec. 31, 2012 FGCO Caa Compliance Claim One IndividualsInAComplaint Complaints	Dec. 31, 2012 FGCO Caa Compliance Claim Two plantiffs	Dec. 31, 2012 JCP&L	Dec. 31, 2011 JCP&L	Dec. 31, 2010 JCP&L	Dec. 31, 2012 JCP&L Regulation of Waste Disposal	Aug. 13, 2012 AE Supply and MP ICG Litigation	May 02, 2011 AE Supply and MP ICG Litigation	Dec. 31, 2012 NGC	Dec. 31, 2012 TE	Feb. 13, 2012 WP	Dec. 31, 2012 WP	Dec. 31, 2012 Parental Guarantees	Dec. 31, 2012 Subsidiaries' Guarantees	Dec. 31, 2012 Other Guarantees	Dec. 31, 2012 State and Local Agencies Hazardous Air Pollutant Emissions	Dec. 31, 2012 Environmental Protection Agency Hazardous Air Pollutant Emissions	Dec. 31, 2012 Transportation Commitment Hazardous Air Pollutant Emissions	Dec. 31, 2012 Minimum Regulation of Waste Disposal	Dec. 31, 2012 Maximum Regulation of Waste Disposal	Dec. 31, 2013 Forecast Nuclear Plant Matters
Guarantor Obligations [Line Items]
Nuclear Insurance Policy, Indemnification, Waiting Period	P26W
Nuclear Insurance Policy, Environmental Plan, Submission Period	30 days
Public Utilities, Liability Asses with Respect to Single Nuclear Incident Based On Act	$ 12,600,000,000
Expected Number of Nuclear Power Plant Licensed to Operate	104
Portion of Insurance Coverage of Private Insurer included in Single Nuclear Incident Liability	375,000,000
Portion of Insurance Coverage by Industry Retrospective Rating Plan	12,200,000,000
Losses in Excess of Private Insurance Contributed for Each Nuclear Unit License	118,000,000
Losses in Excess of Private Insurance Contributed for Each Nuclear Unit License Per Unit	18,000,000
Nuclear Incidence Liability Per Incident of Parent and Subsidiary Companys Based On Their Present Nuclear Ownership and Leasehold Interests	470,000,000																						40,000,000																														408,000,000	22,000,000
Nuclear Incident Liability Not More Than In Any One Year Per Incident of Parent and Subsidiary Companies Based On Their Present Nuclear Ownership and Leasehold Interests	70,000,000																						6,000,000																														61,000,000	3,000,000
Nuclear Insurance Policy, Aggregate Indemnity	2,000,000,000																						168,000,000																														1,700,000,000	90,000,000
Nuclear Insurance Policy, Maximum Aggregate Assessments for Incidents at any Covered Nuclear Facility	14,000,000																						1,000,000																														13,000,000
Coverage of Decontamination Costs As Per Property Damage Insurance	2,750,000,000
Retrospective Assessments Liabilities	69,000,000																						6,000,000																														61,000,000	2,000,000
Insurance Coverage For Replacement Power Costs	1,060,000,000
Outstanding guarantees and other assurances aggregated	4,000,000,000																																																								900,000,000	2,400,000,000	800,000,000
Company posted collateral related to net liability positions																						9,000,000				77,000,000
Potential collateral posted related to net liability positions																										39,000,000				9,000,000
Senior secured term loan facility, term																																3 years			2 years
New syndicated senior secured term loan facility																																	350,000,000
Repayments of senior secured term loan facility	940,000,000	1,909,000,000	1,015,000,000																				0	0	10,000,000	429,000,000	856,000,000	772,000,000								350,000,000			288,000,000	362,000,000	341,000,000						34,000,000	32,000,000	31,000,000
Investment ownership percentage																																		69.99%			33.33%	33.33%
Guarantor obligations, guarantee fee receivable, percentage, remainder of fiscal year																					4.00%
Guarantor obligations, guarantee fee receivable, percentage, next twelve months																					5.00%
Number of complaints filed against FGCO																																												3
Number of complaints seek enjoin plant																																												2	1
Number of individuals behalf of which complaint filed																																													21
Number of named plaintiffs as class representatives																																														8
Reduction in air emissions and compliance												81.00%
Number of electric generation facilities												10
Number of generation units												22
Number of phases under the EPA’s CAIR for reductions of Sulfur Dioxide and Mono-Nitrogen Oxides														2	2
Capping of SO2 emissions (In Tons)													2,500,000
Capping of NOx emissions (In Tons)													1,300,000
Capping of SO2 Emissions Under CSAPR													2,400,000
Capping of NOx emissions under CSAPR													1,200,000
Potential cost of compliance, MATS																975,000,000																																															78,000,000	224,000,000
Waste Disposal, Complaint Period							60 days
Number of coal-fired plants being retired																	9
Pre-tax severance expense related to closures																14,000,000													10,000,000
Upper threshold limit for carbon dioxide emission (Tons per Year)																			75,000
Increase (decrease) in global temperature																		2
Funds provided for Copenhagen Green Climate Fund																		30,000,000,000		100,000,000,000
Commitment Period by Developed Countries to Provide Funds, Years																		3 years
Aspects of opinion reversed						1
Annual percentage that fish impingement should be reduced to, per CWA					12.00%
Loss Contingency, Damages Awarded, Value																																											125,000
Loss Contingency, Damages Awarded, Area of Land in Damages																																											195
Petroleum spills																																										3
Maximum capital investment required to install technology to meet TDS and Sulfate limits					150,000,000
TMDL Limit Development Period					5 years
Number of days required prior to the filing of a citizen suit under notice					60 days
Executed Agreements, Public Comment Period																																											30 days
Claims resolution, civil penalties							800,000																																																86,000
Waste Disposal, Cap Placement Period																																																															6 years	16 years
Options proposed by EPA for additional regulation of coal combustion residuals							2
Total environmental liabilities							124,000,000																																											88,000,000
Environmental Liabilities Former Gas Facilities							81,000,000
Decommissioning Fund Investments	2,204,000,000	2,112,000,000						2,200,000,000	2,200,000,000														141,000,000	137,000,000		1,283,000,000	1,223,000,000												0	0							201,000,000	193,000,000
Parental guarantee associated with the funding of decommissioning costs								95,000,000	95,000,000																																																								135,000,000
Parental Guarantee Associated With Funding Of Decommissioning Costs, Additions								11,000,000
Dismissal Motions Granted										2
Request For Information from Number of Nuclear Power Plants, Total											11
Renewal length of operating license for Davis-Besse Nuclear Power Station									20 years
Final rule, determination period									24 months
Loss incurred in damages for replacement coal purchased																															80,000,000
Additional damages incurred for future shortfalls																															150,000,000
Verdict in Favor																																																				104,000,000
Amount for which verdict entered for future damages																																																				90,000,000
Amount for replacement coal and interest																																																				14,000,000
Gain contingency, unrecorded amount																																																			14,000,000
Potential MATS Extension Period																																																												1 year	1 year
Loss contingency, maximum																																																														60,000,000
Number of allegations remanded to trial court				1
Aspects of opinion under appeal				1
Loss Contingency, Damages Awarded, Compensatory, Value																																																								48,000,000
Loss Contingency, Damages Awarded, Punitive, Value																																																								61,000,000
Gain contingency, damages denied																																																			$ 90,000,000