Commitments, Guarantees and Contingencies (Details Textuals)				1 Months Ended		3 Months Ended		12 Months Ended	51 Months Ended
	Oct. 01, 2015	Aug. 03, 2015 T	Apr. 19, 2013	Jun. 30, 2014	May. 31, 2014	Mar. 31, 2016 USD ($) phases T	Mar. 31, 2015 USD ($) T	Dec. 31, 2014 USD ($)	Mar. 31, 2016 USD ($) T	Dec. 31, 2015 USD ($)	Jun. 30, 2013	Oct. 31, 2012 USD ($)
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated						$ 3,700,000,000			$ 3,700,000,000
New syndicated senior secured term loan facility						$ 406,000,000			406,000,000
Proposed goal to reduce CO2 pollution (percent)						90.00%
Nuclear plant decommissioning trusts						$ 2,360,000,000			2,360,000,000	$ 2,282,000,000
Clean Water Act
Guarantor Obligations [Line Items]
Waste water discharge permit renewal cycle			5 years
Regulation of Waste Disposal
Guarantor Obligations [Line Items]
Bond closure and post closure period						45 years
Period to complete closure						12 years
Accrual for environmental loss contingencies						$ 123,000,000			123,000,000
Environmental liabilities former gas facilities						87,000,000			87,000,000
Nuclear Plant Matters
Guarantor Obligations [Line Items]
Nuclear plant decommissioning trusts						2,400,000,000			2,400,000,000
Parental guarantee						$ 24,500,000			24,500,000
Renewal length of operating license for Davis-Besse Nuclear Power Station						20 years
Caa Compliance
Guarantor Obligations [Line Items]
Loss in period									$ 226,000,000
Amount remaining under contract | T						5,500,000			5,500,000
National Ambient Air Quality Standards
Guarantor Obligations [Line Items]
Capping of SO2 emissions under CSAPR | T						2,400,000
Capping of NOx emissions under CSAPR | T						1,200,000
National Ambient Air Quality Standards | CSAPR
Guarantor Obligations [Line Items]
Number of phases under the EPA’s CAIR for reductions of Sulfur Dioxide and Mono-Nitrogen Oxides | phases						2
Hazardous Air Pollutant Emissions
Guarantor Obligations [Line Items]
Potential cost of compliance, MATS						$ 345,000,000			$ 345,000,000
Climate Change
Guarantor Obligations [Line Items]
Percent reduction in GHG emissions between 2005 and 2012											10.00%
Annual percentage that fish impingement should be reduced to, per CWA					12.00%
Climate Change | Year 2016
Guarantor Obligations [Line Items]
Anticipated reduction in CO2 emissions (percent)											25.00%
Regulated Distribution
Guarantor Obligations [Line Items]
Company posted collateral related to net liability positions						1,000,000			1,000,000
Regulated Distribution | Caa Compliance
Guarantor Obligations [Line Items]
Loss in period									130,000,000
Regulated Distribution | Hazardous Air Pollutant Emissions
Guarantor Obligations [Line Items]
Potential cost of compliance, MATS						177,000,000			177,000,000
Competitive Energy Services | Caa Compliance
Guarantor Obligations [Line Items]
Loss in period									96,000,000
Competitive Energy Services | Hazardous Air Pollutant Emissions
Guarantor Obligations [Line Items]
Potential cost of compliance, MATS						168,000,000			168,000,000
FES
Guarantor Obligations [Line Items]
Company posted collateral related to net liability positions						180,000,000			180,000,000
Potential collateral posted related to net liability positions						3,000,000			3,000,000
New syndicated senior secured term loan facility						25,000,000			25,000,000
Settlement amount								$ 70,000,000
Nuclear plant decommissioning trusts						1,372,000,000			1,372,000,000	$ 1,327,000,000
Global Holding | Senior Secured Term Loan | Senior Loans
Guarantor Obligations [Line Items]
New syndicated senior secured term loan facility						$ 300,000,000	$ 300,000,000		$ 300,000,000			$ 350,000,000
Global Holding | Senior Secured Term Loan | Senior Loans | Signal Peak, Global Rail and Affiliates
Guarantor Obligations [Line Items]
Investment ownership percentage						69.99%			69.99%
FEV | Global Holding
Guarantor Obligations [Line Items]
Loss in period							$ 24,000,000
FEV | Senior Secured Term Loan | Senior Loans | Signal Peak | Global Holding
Guarantor Obligations [Line Items]
Investment ownership percentage						33.33%			33.33%
WMB Marketing Ventures, LLC | Senior Secured Term Loan | Senior Loans | Signal Peak | Global Holding
Guarantor Obligations [Line Items]
Investment ownership percentage						33.33%			33.33%
Environmental Protection Agency | Caa Compliance
Guarantor Obligations [Line Items]
Period of time to implement plan	3 years
Minimum | Clean Water Act
Guarantor Obligations [Line Items]
Maximum capital investment required to install technology to meet TDS and Sulfate limits						$ 150,000,000
Maximum | Clean Water Act
Guarantor Obligations [Line Items]
Maximum capital investment required to install technology to meet TDS and Sulfate limits						300,000,000
Maximum | State and Local Agencies | Climate Change
Guarantor Obligations [Line Items]
Potential MATS extension period				2 years
Put Option | FEV | Signal Peak
Guarantor Obligations [Line Items]
Derivative notional amount mass (tons) | T							2,000,000
Certain Coal-Fired Power Plant | FirstEnergy Generation LLC | Mercury and Air Toxic Standards
Guarantor Obligations [Line Items]
Minimum coal supply commitment (ton) | T		3,500,000.0
Another Coal-Fired Power Plant | FirstEnergy Generation LLC | Mercury and Air Toxic Standards
Guarantor Obligations [Line Items]
Minimum coal supply commitment (ton) | T		2,500,000.0
FirstEnergy
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated						591,000,000			$ 591,000,000
Subsidiaries
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated						2,100,000,000			2,100,000,000
Other Guarantee
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated						300,000,000			300,000,000
Other Assurances
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated						$ 669,000,000			$ 669,000,000