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Commitments, Guarantees and Contingencies (Details Textuals)			1 Months Ended		6 Months Ended	9 Months Ended	12 Months Ended	54 Months Ended
	Oct. 01, 2015	Aug. 03, 2015 T	Jun. 30, 2014	May 31, 2014	Jun. 30, 2016 USD ($) phases T	Sep. 30, 2015	Dec. 31, 2014 USD ($)	Jun. 30, 2016 USD ($) T	Dec. 31, 2015 USD ($)	Oct. 31, 2012 USD ($)
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated					$ 3,500,000,000			$ 3,500,000,000
New syndicated senior secured term loan facility					$ 379,000,000			379,000,000
Proposed goal to reduce CO2 pollution (percent)					90.00%
Nuclear plant decommissioning trusts					$ 2,456,000,000			2,456,000,000	$ 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					$ 124,000,000			124,000,000
Environmental liabilities former gas facilities					89,000,000			89,000,000
Nuclear Plant Matters
Guarantor Obligations [Line Items]
Nuclear plant decommissioning trusts					2,500,000,000			2,500,000,000
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								$ 253,000,000
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]
Annual percentage that fish impingement should be reduced to, per CWA				12.00%
Regulated Distribution \| Caa Compliance
Guarantor Obligations [Line Items]
Loss in period								145,000,000
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								108,000,000
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					145,000,000			145,000,000
Settlement amount							$ 70,000,000
Nuclear plant decommissioning trusts					1,510,000,000			1,510,000,000	$ 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		$ 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 \| 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
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					590,000,000			$ 590,000,000
Subsidiaries
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated					2,000,000,000			2,000,000,000
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					$ 597,000,000			$ 597,000,000