Commitments, Guarantees and Contingencies (Details Textuals) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended		0 Months Ended	6 Months Ended	1 Months Ended	6 Months Ended		6 Months Ended					6 Months Ended			6 Months Ended			3 Months Ended	6 Months Ended				6 Months Ended	3 Months Ended			3 Months Ended	6 Months Ended			6 Months Ended			6 Months Ended					0 Months Ended				3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 ICG Litigation	Jun. 30, 2013 Clean Water Act	Apr. 30, 2009 Clean Water Act aspect_of_opinion	Mar. 28, 2013 Regulation of Waste Disposal	Jun. 30, 2013 Regulation of Waste Disposal options	May 31, 2013 Nuclear Plant Matters petitioners	Jun. 30, 2013 Nuclear Plant Matters	Dec. 28, 2012 Nuclear Plant Matters decision	Jun. 30, 2013 Caa Compliance CoalFiredPlants ElectricGenerationUnits	Jun. 30, 2013 National Ambient Air Quality Standards T	Jun. 30, 2013 National Ambient Air Quality Standards CAIR phases	Jun. 30, 2013 National Ambient Air Quality Standards CSAPR phases	Jun. 30, 2013 Hazardous Air Pollutant Emissions	Jun. 30, 2013 Climate Change celsius	Apr. 13, 2012 Climate Change lb	Jan. 02, 2011 Climate Change T	Jun. 30, 2013 Climate Change Year 2020 Increase in funding	Jun. 30, 2013 Senior Secured Term Loan Senior Loans	Jun. 30, 2013 Regulated Distribution	Jun. 30, 2012 FES	Jun. 30, 2013 FES	Jun. 30, 2012 FES	Dec. 31, 2012 FES	Jun. 30, 2013 AE Supply	Jun. 30, 2013 AE Supply ICG Litigation	Jun. 30, 2013 Global Holding	Jun. 30, 2013 Global Holding Senior Secured Term Loan Senior Loans	Jun. 30, 2013 Global Holding Senior Secured Term Loan Senior Loans Signal Peak, Global Rail and Affiliates	Jun. 30, 2013 Signal Peak and Global Rail	Jun. 30, 2013 Signal Peak and Global Rail Senior Secured Term Loan Senior Loans	Jun. 30, 2013 FEV Senior Secured Term Loan Senior Loans Signal Peak Global Holding	Jun. 30, 2013 WMB Marketing Ventures, LLC Senior Secured Term Loan Senior Loans Signal Peak Global Holding	Jun. 30, 2013 FGCO	Jun. 30, 2012 FGCO	Dec. 31, 2012 FGCO	Jun. 30, 2013 FGCO Caa Compliance Complaints	Jun. 30, 2013 FGCO Caa Compliance Claim One IndividualsInAComplaint Complaints	Jun. 30, 2013 FGCO Caa Compliance Claim Two plantiffs	Aug. 13, 2012 AE Supply and MP ICG Litigation	May 02, 2011 AE Supply and MP ICG Litigation	Feb. 13, 2012 Wp	Jun. 30, 2013 Parental Guarantees	Jun. 30, 2013 Subsidiaries' Guarantees	Jun. 30, 2013 Other Guarantees	Jun. 30, 2013 State and Local Agencies Hazardous Air Pollutant Emissions	Jun. 30, 2013 Environmental Protection Agency Hazardous Air Pollutant Emissions	Apr. 13, 2012 Minimum Climate Change	Apr. 13, 2012 Maximum Climate Change	Jun. 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	$ 3,900,000,000		$ 3,900,000,000																																												$ 895,000,000	$ 2,240,000,000	$ 725,000,000
Company posted collateral related to net liability positions																								17,000,000		86,000,000
Potential collateral posted related to net liability positions																										86,000,000			3,000,000
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			1,968,000,000	746,000,000																						1,179,000,000	140,000,000								350,000,000			352,000,000	63,000,000
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%																																						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								650,000,000
Loss Contingency, Settlement Agreement, Consideration																																																							45,000,000
Loss Contingency, Range of Possible Loss, Maximum																																																						22,000,000
Pre-tax severance expense related to closures	15,000,000	10,000,000		17,000,000																					6,000,000		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
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
Accrual for Environmental Loss Contingencies										124,000,000
Environmental Liabilities Former Gas Facilities										82,000,000
Decommissioning Fund Investments	2,178,000,000		2,178,000,000		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
Dismissal Motions Granted													2
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
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