Organization and Basis of Presentation (Details Textuals) mi in Thousands, customer in Millions, MWh in Millions				1 Months Ended	3 Months Ended			12 Months Ended
	Feb. 17, 2017 USD ($) Natural_gas_plant	Jan. 18, 2017 USD ($) Natural_gas_plant MW	Jul. 19, 2016 MW	Feb. 21, 2017 MWh MW	Dec. 31, 2016 USD ($) transmission_center MW	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2018 USD ($) MWh	Dec. 31, 2017 USD ($) MWh	Dec. 31, 2016 USD ($) MWh customer transmission_center company mi MW	Dec. 31, 2015 USD ($) MW	Dec. 31, 2014 USD ($)	Jan. 31, 2017 USD ($) MW	Dec. 06, 2016 USD ($)	Dec. 05, 2016 USD ($)	Oct. 09, 2013 MW
Regulatory Assets [Line Items]
Aggregate amount of capacity (in MWs) | MW										17,000
Length of transmission lines | mi										24
Number of regional transmission centers | transmission_center					2					2
Impairment							$ 800,000,000			$ 800,000,000
Regulatory assets that do not earn a current return					$ 153,000,000					153,000,000	$ 148,000,000
Net regulatory liabilities					157,000,000					157,000,000	116,000,000
Capitalized financing costs										37,000,000	49,000,000	$ 49,000,000
Interest costs capitalized										66,000,000	68,000,000	69,000,000
Net plant in progress					28,036,000,000					28,036,000,000	34,792,000,000
Other than temporary impairments										21,000,000	102,000,000	37,000,000
Impairments of long-lived assets										$ (10,665,000,000)	(42,000,000)	0
Regulated Distribution
Regulatory Assets [Line Items]
Number of existing utility operating companies | company										10
Number of customers served by utility operating companies | customer										6
Impairment										$ 0
Plant generation capacity (in MW's) | MW																3,790
Property, plant and equipment, net					2,100,000,000					2,100,000,000
Net plant in progress					17,810,000,000					17,810,000,000	$ 17,169,000,000
Competitive Energy Services
Regulatory Assets [Line Items]
Deactivated power plants (in MW) | MW											6,770
Impairment										$ 800,000,000
Impairment of assets					$ 9,218,000,000		647,000,000
Plant generation capacity (in MW's) | MW					13,162					13,162
Purchase power agreements additional capacity (in MWh) | MWh										5
Contract sales (in MWh) | MWh										53
Net plant in progress					$ 2,413,000,000					$ 2,413,000,000	$ 11,001,000,000
Bath County, Virginia
Regulatory Assets [Line Items]
Plant generation capacity (in MW's) | MW					3,003					3,003
MP
Regulatory Assets [Line Items]
Maximum amount borrowed under revolving credit facility					$ 500,000,000					$ 500,000,000
Ownership interest (percent)										41.00%
Virginia Electric and Power Company | Bath County, Virginia
Regulatory Assets [Line Items]
Proportionate ownership share (percent)					60.00%					60.00%
FES
Regulatory Assets [Line Items]
Impairment							23,000,000			$ 23,000,000
Interest costs capitalized										34,000,000	35,000,000	34,000,000
Net plant in progress					$ 1,128,000,000					1,128,000,000	8,546,000,000
Other than temporary impairments										19,000,000	90,000,000	33,000,000
Impairments of long-lived assets										(8,622,000,000)	(33,000,000)	$ 0
FES | Competitive Energy Services
Regulatory Assets [Line Items]
Impairment of assets					8,082,000,000		$ 517,000,000
AGC | Competitive Energy Services
Regulatory Assets [Line Items]
Net plant in progress					$ 458,000,000					$ 458,000,000
AGC | Bath County, Virginia
Regulatory Assets [Line Items]
Plant generation capacity (in MW's) | MW					1,200					1,200
Proportionate ownership share (percent)					40.00%					40.00%
Net plant in progress					$ 639,000,000					$ 639,000,000
Signal Peak | Global Holding | FEV
Regulatory Assets [Line Items]
Impairments of long-lived assets											(362,000,000)
Bay Shore Unit 1
Regulatory Assets [Line Items]
Plant capacity (in MW's) | MW			136
Sammis Power Plant Units 1-4
Regulatory Assets [Line Items]
Plant capacity (in MW's) | MW			720
Pleasants Power Station | Competitive Energy Services
Regulatory Assets [Line Items]
Plant generation capacity (in MW's) | MW					1,300					1,300
Forecast | Competitive Energy Services
Regulatory Assets [Line Items]
Plant generation capacity (in MW's) | MW				10,000
Forecast | FES | Competitive Energy Services
Regulatory Assets [Line Items]
Debt that needs to be refinanced								$ 515,000,000	$ 130,000,000
Purchase Agreement with Aspen Generating, LLC
Regulatory Assets [Line Items]
Plant generation capacity (in MW's) | MW					1,572					1,572
Purchase Agreement with Aspen Generating, LLC | AE Supply
Regulatory Assets [Line Items]
Ownership interest (percent)										59.00%
Subsequent Event
Regulatory Assets [Line Items]
Maximum amount borrowed under revolving credit facility													$ 5,000,000,000
Subsequent Event | FES
Regulatory Assets [Line Items]
Maximum amount borrowed under revolving credit facility													$ 500,000,000
Subsequent Event | Pleasants Power Station
Regulatory Assets [Line Items]
Plant generation capacity (in MW's) | MW													1,300
Subsequent Event | Held-for-sale | Pleasants Power Station
Regulatory Assets [Line Items]
Assets held for sale													$ 195,000,000
Subsequent Event | Purchase Agreement with Aspen Generating, LLC
Regulatory Assets [Line Items]
Plant generation capacity (in MW's) | MW		1,572
Cash purchase price	$ 925,000,000	$ 925,000,000
Subsequent Event | Purchase Agreement with Aspen Generating, LLC | AE Supply
Regulatory Assets [Line Items]
Number of gas generating plants | Natural_gas_plant	4	4
Discharge of note indenture		$ 305,000,000
Make-whole premiums		$ 100,000,000
Subsequent Event | Purchase Agreement with Aspen Generating, LLC | AE Supply | Bath County, Virginia
Regulatory Assets [Line Items]
Proportionate ownership share (percent)		23.75%
Line of Credit | Revolving Credit Facility
Regulatory Assets [Line Items]
Maximum amount borrowed under revolving credit facility					$ 500,000,000					$ 500,000,000				$ 4,000,000,000	$ 3,500,000,000.0
Line of Credit | Revolving Credit Facility | AE Supply
Regulatory Assets [Line Items]
Maximum amount borrowed under revolving credit facility															600,000,000
Line of Credit | Revolving Credit Facility | FES
Regulatory Assets [Line Items]
Maximum amount borrowed under revolving credit facility															$ 900,000,000
Line of Credit | Revolving Credit Facility | Subsequent Event
Regulatory Assets [Line Items]
Maximum amount borrowed under revolving credit facility													5,000,000,000
Line of Credit | Revolving Credit Facility | Subsequent Event | FES
Regulatory Assets [Line Items]
Maximum amount borrowed under revolving credit facility													$ 500,000,000
Minimum | Competitive Energy Services
Regulatory Assets [Line Items]
Annual generation capacity (in MW) | MWh										70
Minimum | Forecast | Competitive Energy Services
Regulatory Assets [Line Items]
Annual generation capacity (in MW) | MWh				60
Expected contract sales (in MWh) | MWh								35	40
Maximum | Competitive Energy Services
Regulatory Assets [Line Items]
Annual generation capacity (in MW) | MWh										75
Maximum | Forecast | Competitive Energy Services
Regulatory Assets [Line Items]
Annual generation capacity (in MW) | MWh				65
Expected contract sales (in MWh) | MWh								40	45
Utilization of Accelerated Useful Life
Regulatory Assets [Line Items]
Out-of period adjustment						$ 21,000,000					$ 19,000,000