Asset Sales and Impairments (Details 1)					1 Months Ended		3 Months Ended								6 Months Ended	12 Months Ended
	Dec. 13, 2017 USD ($)	Oct. 20, 2017	Aug. 30, 2017 USD ($) limited_guaranty Natural_gas_plant	Jul. 22, 2016 MW	Aug. 31, 2017 USD ($) Natural_gas_plant MW	Jan. 31, 2017 USD ($) MW	Dec. 31, 2017 USD ($) MW	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($) MW	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 06, 2017 USD ($) MW
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets																		$ 42,000,000
Potential collateral obligations							$ 407,000,000									$ 407,000,000
Impairments of long-lived assets																2,406,000,000	$ 10,665,000,000	42,000,000
Impairment of assets and related charges (Note 2)							$ 2,244,000,000	$ 31,000,000	$ 131,000,000	$ 0	$ 9,218,000,000	$ 0	$ 1,447,000,000	$ 0		$ 2,406,000,000	10,665,000,000	42,000,000
Impairment													800,000,000				800,000,000
Contract Termination
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restructuring charges													58,000,000
CES
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets											9,218,000,000							34,000,000
Plant generation capacity (in MW's) | MW							12,303									12,303
Impairment of assets																$ 193,000,000
Impairment of assets and related charges (Note 2)													647,000,000			$ 2,365,000,000	$ 10,665,000,000	34,000,000
CES | Income Approach Valuation Technique | Goodwill
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate (percent)																	9.50%
Terminal value of EBITDA																	7.0
Regulated Distribution
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets																		8,000,000
Plant generation capacity (in MW's) | MW							3,790									3,790
Potential collateral obligations							$ 148,000,000									$ 148,000,000
Impairment of assets and related charges (Note 2)																0	$ 0	8,000,000
AE Supply
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Potential collateral obligations							2,000,000									2,000,000
FES
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets							2,045,000,000											33,000,000
Potential collateral obligations							20,000,000									20,000,000
Impairments of long-lived assets																2,031,000,000	8,622,000,000	33,000,000
Impairment of assets and related charges (Note 2)							2,031,000,000	0	$ 0	$ 0	8,082,000,000	$ 0	540,000,000	$ 0		2,031,000,000	8,622,000,000	$ 33,000,000
Impairment													23,000,000				$ 23,000,000
FES | CES
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets							2,000,000,000				$ 8,082,000,000
Potential collateral obligations							2,000,000									2,000,000
Impairment of assets							2,000,000,000
Impairment of assets and related charges (Note 2)													$ 517,000,000
MAIT
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairments of long-lived assets								$ 13,000,000
Pleasants Power Station
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets							120,000,000
Plant generation capacity (in MW's) | MW																			1,300
Assets purchase agreement consideration to be received																			$ 195,000,000
Carrying value of power station							$ 75,000,000									$ 75,000,000
Bay Shore Unit 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Plant capacity (in MW's) | MW				136
Sammis Power Plant Units 1-4
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Plant capacity (in MW's) | MW				720
Purchase Agreement with Subsidiary of LS Power
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Plant generation capacity (in MW's) | MW					1,615		756									756
Plant capacity (in MW's) | MW						1,615
Cash purchase price					$ 825,000,000	$ 825,000,000
Number of limited guaranties | limited_guaranty			2
Term of guaranties			3 years
Purchase Agreement with Subsidiary of LS Power | AE Supply
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of gas generating plants | Natural_gas_plant			4		4
Discharge of note indenture			$ 305,000,000
Make-whole premiums																$ 95,000,000
Purchase Agreement with Subsidiary of LS Power | AGC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Plant ownership percentage		59.00%	59.00%		59.00%
Make-whole premiums																95,000,000
Purchase Agreement with Subsidiary of LS Power | Natural Gas Generating Plants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash purchase price	$ 388,000,000
Held-for-sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets held-for-sale							$ 354,000,000									354,000,000
Investments							19,000,000									19,000,000
Materials and supplies inventory							2,000,000									2,000,000
Forecast | Purchase Agreement with Subsidiary of LS Power | Bath County Hydroelectric Power Station and Buchanan Generating Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash purchase price															$ 375,000,000
FE
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Potential collateral obligations							237,000,000									$ 237,000,000
FE | Purchase Agreement with Subsidiary of LS Power
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Potential collateral obligations	$ 555,000,000
Purchase Agreement Guarantee, Breaches of Covenants and Indebtedness | FE | Purchase Agreement with Subsidiary of LS Power
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Term of guaranties	3 years
Potential collateral obligations	$ 463,000,000
Purchase Agreement Guarantee, Breaches of Non-fundamental Representations | FE | Purchase Agreement with Subsidiary of LS Power
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Potential collateral obligations	$ 92,000,000
Senior Notes | Purchase Agreement with Subsidiary of LS Power | AGC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discharge of note indenture			$ 100,000,000
PCRB | Purchase Agreement with Subsidiary of LS Power | AE Supply
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discharge of note indenture			$ 142,000,000
FERC | JCP&L
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairments of long-lived assets							$ 28,000,000