Commitments, Guarantees and Contingencies (Details Textuals) (USD $)	3 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended		0 Months Ended	9 Months Ended	0 Months Ended		1 Months Ended	9 Months Ended						9 Months Ended			9 Months Ended				9 Months Ended				9 Months Ended	3 Months Ended			3 Months Ended	9 Months Ended			9 Months Ended			9 Months Ended					0 Months Ended				3 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 ICG Litigation	Sep. 30, 2013 Clean Water Act	Apr. 30, 2009 Clean Water Act aspect_of_opinion	Mar. 28, 2013 Regulation of Waste Disposal	Sep. 30, 2013 Regulation of Waste Disposal options	Oct. 10, 2013 Regulation of Waste Disposal Subsequent Event IndividualsInAComplaint	Oct. 03, 2013 Regulation of Waste Disposal Subsequent Event deficiency	May 31, 2013 Nuclear Plant Matters petitioners	Sep. 30, 2013 Nuclear Plant Matters	Sep. 30, 2013 Caa Compliance CoalFiredPlants ElectricGenerationUnits	Sep. 30, 2013 National Ambient Air Quality Standards T	Sep. 30, 2013 National Ambient Air Quality Standards CAIR phases	Sep. 30, 2013 National Ambient Air Quality Standards CSAPR phases	Sep. 30, 2013 Hazardous Air Pollutant Emissions	Sep. 30, 2013 Climate Change celsius	Apr. 13, 2012 Climate Change lb	Jan. 02, 2011 Climate Change T	Sep. 30, 2013 Climate Change Year 2020 Increase in funding	Sep. 30, 2013 Senior Secured Term Loan Senior Loans	Dec. 31, 2012 Senior Secured Term Loan Senior Loans	Sep. 30, 2013 Regulated Distribution	Sep. 30, 2013 FES	Sep. 30, 2012 FES	Dec. 31, 2012 FES	Sep. 30, 2013 AE Supply	Sep. 30, 2013 AE Supply ICG Litigation	Sep. 30, 2013 Global Holding	Sep. 30, 2013 Global Holding Senior Secured Term Loan Senior Loans	Sep. 30, 2013 Global Holding Senior Secured Term Loan Senior Loans Signal Peak, Global Rail and Affiliates	Sep. 30, 2013 Signal Peak and Global Rail	Sep. 30, 2013 Signal Peak and Global Rail Senior Secured Term Loan Senior Loans	Sep. 30, 2013 FEV Senior Secured Term Loan Senior Loans Signal Peak Global Holding	Sep. 30, 2013 WMB Marketing Ventures, LLC Senior Secured Term Loan Senior Loans Signal Peak Global Holding	Sep. 30, 2013 FGCO	Sep. 30, 2012 FGCO	Dec. 31, 2012 FGCO	Sep. 30, 2013 FGCO Caa Compliance Complaints	Sep. 30, 2013 FGCO Caa Compliance Claim One IndividualsInAComplaint Complaints	Sep. 30, 2013 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	Sep. 30, 2013 Parental Guarantees	Sep. 30, 2013 Subsidiaries' Guarantees	Sep. 30, 2013 Other Guarantees	Sep. 30, 2013 State and Local Agencies Hazardous Air Pollutant Emissions	Sep. 30, 2013 Environmental Protection Agency Hazardous Air Pollutant Emissions	Apr. 13, 2012 Minimum Climate Change	Apr. 13, 2012 Maximum Climate Change	Sep. 30, 2013 Transportation Commitment [Member] Hazardous Air Pollutant Emissions	Dec. 31, 2012 Transportation Commitment [Member] Hazardous Air Pollutant Emissions
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated	$ 4,400,000,000	$ 4,400,000,000																																													$ 1,403,000,000	$ 2,232,000,000	$ 747,000,000
Company posted collateral related to net liability positions																									16,000,000	150,000,000			8,000,000
Potential collateral posted related to net liability positions																										77,000,000			2,000,000
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		2,662,000,000	870,000,000																							1,179,000,000	246,000,000								350,000,000			352,000,000	169,000,000
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										50																																21
Number of named plaintiffs as class representatives																																											8
Reduction in air emissions and compliance																																																				25.00%	40.00%
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									234,000,000									465,000,000
Loss Contingency, Settlement Agreement, Consideration																																																							45,000,000
Loss Contingency, Range of Possible Loss, Maximum																																																						25,000,000
Pre-tax severance expense related to closures	2,000,000		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
Commitment, Proposed Emissions Standard																				1,000
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
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								15 years			9 years
Bond Closure and Post Closure Period											45 years
Accrual for Environmental Loss Contingencies									124,000,000
Environmental Liabilities Former Gas Facilities									82,000,000
Decommissioning Fund Investments	2,183,000,000	2,183,000,000		2,204,000,000									2,200,000,000													1,270,000,000		1,283,000,000										0		0
Parental guarantee associated with the funding of decommissioning costs													125,000,000
Parental Guarantee Associated With Funding Of Decommissioning Costs, Additions													11,000,000
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
Gain contingency, damages denied					$ 16,000,000
Number of Petitioners												4