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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 |  |  |  |  |

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