Commitments, Guarantees and Contingencies (Details Textuals) (USD $)	3 Months Ended				3 Months Ended		12 Months Ended			0 Months Ended				3 Months Ended	0 Months Ended	1 Months Ended	3 Months Ended						3 Months Ended						3 Months Ended					3 Months Ended			0 Months Ended		3 Months Ended				3 Months Ended				3 Months Ended			0 Months Ended	3 Months Ended					0 Months Ended				3 Months Ended				3 Months Ended		3 Months Ended	12 Months Ended	1 Months Ended		12 Months Ended		0 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Jan. 31, 2009	Jun. 30, 2013 ICG Litigation	Mar. 31, 2014 Clean Water Act	Dec. 31, 2013 Clean Water Act	Apr. 19, 2013 Clean Water Act options	Apr. 30, 2009 Clean Water Act aspect_of_opinion	Apr. 16, 2014 Clean Water Act Subsequent Event	Oct. 10, 2013 Regulation of Waste Disposal IndividualsInAComplaint	Oct. 03, 2013 Regulation of Waste Disposal deficiency	Mar. 28, 2013 Regulation of Waste Disposal	Mar. 31, 2014 Regulation of Waste Disposal options	Apr. 03, 2014 Regulation of Waste Disposal Subsequent Event	May 31, 2013 Nuclear Plant Matters petitioners	Mar. 31, 2014 Nuclear Plant Matters	Mar. 31, 2014 Caa Compliance ElectricGenerationUnits CoalFiredPlants	Mar. 31, 2014 National Ambient Air Quality Standards T	Mar. 31, 2014 National Ambient Air Quality Standards CAIR phases	Mar. 31, 2014 National Ambient Air Quality Standards CSAPR phases	Mar. 31, 2014 Hazardous Air Pollutant Emissions	Mar. 31, 2014 Climate Change celsius	Jun. 30, 2013 Climate Change	Apr. 13, 2012 Climate Change lb	Jan. 02, 2011 Climate Change T	Jun. 30, 2013 Climate Change Year 2016	Jun. 30, 2013 Climate Change Year 2020	Mar. 31, 2014 Climate Change Year 2020 Increase in funding	Mar. 31, 2014 Senior Secured Term Loan Senior Loans	Mar. 31, 2014 Regulated Distribution	Mar. 31, 2014 Regulated Distribution Hazardous Air Pollutant Emissions	Mar. 31, 2014 Competitive Energy Services Hazardous Air Pollutant Emissions	Mar. 31, 2014 FES	Mar. 31, 2013 FES	Dec. 31, 2013 FES	Apr. 16, 2014 FES Subsequent Event	Mar. 31, 2014 AE Supply	Mar. 31, 2014 AE Supply ICG Litigation	Mar. 31, 2014 Global Holding	Mar. 31, 2014 Global Holding Senior Secured Term Loan Senior Loans	Mar. 31, 2014 Global Holding Senior Secured Term Loan Senior Loans Signal Peak, Global Rail and Affiliates	Mar. 31, 2014 Signal Peak and Global Rail	Mar. 31, 2014 Signal Peak and Global Rail Senior Secured Term Loan Senior Loans	Mar. 31, 2014 FEV Senior Secured Term Loan Senior Loans Signal Peak Global Holding	Mar. 31, 2014 WMB Marketing Ventures, LLC Senior Secured Term Loan Senior Loans Signal Peak Global Holding	Mar. 31, 2014 FGCO	Mar. 31, 2013 FGCO	Dec. 31, 2013 FGCO	Dec. 05, 2013 FGCO Regulation of Waste Disposal IndividualsInAComplaint	Mar. 31, 2014 FGCO Caa Compliance Complaints	Mar. 31, 2014 FGCO Caa Compliance Claim One IndividualsInAComplaint Complaints	Mar. 31, 2014 FGCO Caa Compliance Claim Two plaintiff	Aug. 13, 2012 AE Supply and MP ICG Litigation	May 02, 2011 AE Supply and MP ICG Litigation	Feb. 13, 2012 WP	Mar. 31, 2014 Parental Guarantees	Mar. 31, 2014 Subsidiaries' Guarantees	Mar. 31, 2014 Other Guarantees	Mar. 31, 2014 State and Local Agencies Hazardous Air Pollutant Emissions	Mar. 31, 2014 Environmental Protection Agency Hazardous Air Pollutant Emissions	Mar. 31, 2014 Minimum Clean Water Act	Apr. 13, 2012 Minimum Climate Change	Mar. 31, 2014 Maximum Clean Water Act	Apr. 13, 2012 Maximum Climate Change	Dec. 31, 2013 Transportation Commitment Hazardous Air Pollutant Emissions	Dec. 31, 2012 Transportation Commitment Hazardous Air Pollutant Emissions contracts	Jan. 31, 2014 Mepco Holdings,LLC Hazardous Air Pollutant Emissions	Mar. 31, 2014 Beaver Valley Unit 1 and Perry Nuclear Plant Matters	Dec. 31, 2013 Little Blue Run Regulation of Waste Disposal	Feb. 01, 2014 Davis-Besse Nuclear Power Station fuel_assembly stream_generator	Feb. 01, 2014 Davis-Besse Nuclear Power Station FES
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated	$ 4,000,000,000																																																								$ 896,000,000	$ 2,207,000,000	$ 891,000,000
Company posted collateral related to net liability positions																															28,000,000			544,000,000				8,000,000
Proceeds from return of collateral																																					275,000,000
Potential collateral posted related to net liability positions																																		111,000,000				1,000,000
New syndicated senior secured term loan facility																																									350,000,000
Repayments of senior secured term loan facility	489,000,000	846,000,000																																445,000,000	476,000,000									350,000,000			248,000,000	107,000,000
Senior secured term loan facility, term																																								3 years			2 years
Investment ownership percentage																																										69.99%			33.33%	33.33%
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											50																																							15		21
Number of named plaintiffs as class representatives																																																					8
Jointly owned utility plant, proportionate ownership share				16.67%
Reduction in air emissions and compliance																																																															25.00%		40.00%
Additional Regulation Finalization Period										29 days
Number of treatment options								8
Number of preferred treatment options								4
Waste water discharge permit renewal cycle							5 years
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														234,000,000								465,000,000										225,000,000	240,000,000
Loss Contingency, Settlement Agreement, Consideration																																																																		67,000,000	70,000,000	18,000,000
Percent reduction in GHG Emissions Between 2005 And 2012																								10.00%
Anticipated Reduction in CO2 Emissions (Percent)																											25.00%
Proposed Executive Action, Reduction in Power Plants Carbon Pollution, Percentage																												17.00%
Proposed emissions standard of large natural gas fired units																									1,000
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
Commitment, Proposed Emissions Standard, Other Natural Gas Fired Units																									1,100
Commitment, Proposed Emissions Standard, Fossil Fuel Fired Units																									1,100
Aspects of opinion reversed									1
Annual percentage that fish impingement should be reduced to, per CWA						12.00%
Maximum capital investment required to install technology to meet TDS and Sulfate limits																																																														150,000,000		300,000,000
TMDL Limit Development Period						5 years
Number of Deficiencies Identified in Plan												4
Options proposed by EPA for additional regulation of coal combustion residuals														2
Claims Resolution, Civil Penalties														800,000																																										86,000
Period of time to implement plan												9 years	15 years
Bond Closure and Post Closure Period												45 years
Asset Retirement Obligation, Period Increase (Decrease)																																																																						163,000,000
Permit to Provide Bonding for Closure and Post-Closure Activities															45 years
Period to Complete Closure															12 years
Accrual for Environmental Loss Contingencies														129,000,000
Environmental Liabilities Former Gas Facilities														82,000,000
Decommissioning Fund Investments	2,263,000,000		2,201,000,000														2,300,000,000																	1,323,000,000		1,276,000,000											0		0
Parental guarantee associated with the funding of decommissioning costs																	125,000,000																																																				9,500,000
Parental Guarantee Associated With Funding Of Decommissioning Costs, Additions																	11,000,000
Parental Guarantee Associated With Funding Of Decommissioning Costs, Next Fiscal Quarter																	155,000,000
Renewal length of operating license for Davis-Besse Nuclear Power Station																	20 years
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
Gain Contingency, Damages Denied, Value																																																						90,000,000
Potential MATS Extension Period																																																												1 year	1 year
Loss Contingency, Claims Settled Number																																																																			2
Gain contingency, damages denied					15,500,000
Number of Petitioners																2
Number of Steam Generators to Be Installed																																																																							2
Number of Fuel Assemblies to Be Replaced, Percent																																																																							33.33%
Number of Fuel Assemblies																																																																							177
Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses																																																																								$ 600,000,000