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Commitments and Contingencies (Environmental Matters and Other Legal Matters) (Narrative) (Details) | 1 Months Ended | 3 Months Ended | 12 Months Ended
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Apr. 30, 2017 | Nov. 30, 2016 USD ($) | Jul. 31, 2016 party | Jun. 30, 2016 party | Apr. 30, 2016 USD ($) | Oct. 31, 2015 | Jun. 30, 2015 party | Apr. 30, 2015 facility | Oct. 31, 2014 facility | Jun. 30, 2014 unit | Jul. 31, 2013 unit | Sep. 30, 2011 party | Jul. 31, 2011 state group MW | Mar. 31, 2016 party | Dec. 31, 2016 USD ($) facility party site | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($)
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Charges associated with future ash pond and landfill closure costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 197,000,000 |  | $ 99,000,000 |  | $ 121,000,000
ARO recorded related to future ash pond and landfill closure costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 204,000,000 | [1] | 315,000,000 | [2] |
Legislation enacted | EPA | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period for consideration of CO2 emissions for biomass projects |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |
Virginia Electric and Power Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Charges associated with future ash pond and landfill closure costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 197,000,000 |  | 99,000,000 |  | 121,000,000
ARO recorded related to future ash pond and landfill closure costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9,000,000 |  | 289,000,000 | [2] |
Virginia Electric and Power Company | Legislation enacted | EPA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of coal fired generating units | unit |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |  |  |
DTI | Breach of Contract Lawsuit | Pending Litigation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of accrued liability |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 6,000,000 |  |  |  |
Cove Point | Liquefaction Project | FERC | Pending Litigation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of parties | party |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |
Cove Point | Liquefaction Project | FERC | Judicial Ruling |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of parties | party |  |  | 1 |  |  |  | 1 |  |  |  |  |  |  |  |  |  |  |  |
Dominion Gas Holdings, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ARO recorded related to future ash pond and landfill closure costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 6,000,000 |  | 5,000,000 |  |
MATS | Legislation enacted | EPA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Compliance extension period |  |  |  |  |  |  |  |  |  | 1 year |  |  |  |  |  |  |  |  |
Number of coal fired generating units | unit |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |
Compliance extension period |  |  |  |  |  | 1 year |  |  |  |  |  |  |  |  |  |  |  |  |
MATS | Legislation enacted | EPA | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Compliance extension period |  |  |  |  | 1 year |  |  |  |  |  |  |  |  |  |  |  |  |  |
MATS | Legislation enacted | EPA | Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period to be in service following receipt of all required permits | 20 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
CSAPR | Legislation enacted | EPA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of states under EPA Replacement Rule | state |  |  |  |  |  |  |  |  |  |  |  |  | 28 |  |  |  |  |  |
Number of groups of affected states | group |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |
CSAPR | Legislation enacted | EPA | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Emissions of fossil fuel fired electric generating units | MW |  |  |  |  |  |  |  |  |  |  |  |  | 25 |  |  |  |  |  |
Ozone Standards | Legislation enacted | EPA | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated compliance costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 25,000,000 |  |  |  |
Ozone Standards | Legislation enacted | EPA | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated compliance costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 35,000,000 |  |  |  |
NOx and VOC Emissions | Dominion Gas Holdings, LLC | Legislation enacted | Pennsylvania Department of Environmental Protection |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated compliance costs |  |  |  |  | $ 25,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
CERCLA | Legislation enacted | EPA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of parties ordered specific remedial action | party |  |  |  |  |  |  |  |  |  |  |  | 22 |  |  |  |  |  |  |
CERCLA | Virginia Electric and Power Company | Legislation enacted | EPA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash settlement amount (less than $1 million) |  | $ 1,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Coal Tar and Other Potentially Harmful Materials | Legislation enacted | EPA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of former manufactured gas plant sites | site |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 19 |  |  |  |
Coal Tar and Other Potentially Harmful Materials | Legislation enacted | EPA | Former Gas Plant Site with Post Closure Groundwater Monitoring Program |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number sites | site |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |
Coal Tar and Other Potentially Harmful Materials | Virginia Electric and Power Company | Legislation enacted | EPA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of former manufactured gas plant sites | site |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |
Estimates for compliance, minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,000,000 |  |  |  |
Estimates for compliance, maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 22,000,000 |  |  |  |
Coal Tar and Other Potentially Harmful Materials | Dominion Gas Holdings, LLC | Legislation enacted | EPA |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of former manufactured gas plant sites | site |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 12 |  |  |  |
Clean Water Act | Legislation enacted |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of facilities | facility |  |  |  |  |  |  |  |  | 14 |  |  |  |  |  |  |  |  |  |
Clean Water Act | Legislation enacted | EPA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of facilities subject to ruling | facility |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8 |  |  |  |
Clean Water Act | Virginia Electric and Power Company | Possum Point Power Station | Other operations and maintenance expense |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Charges associated with future ash pond and landfill closure costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 121,000,000
Clean Water Act | Virginia Electric and Power Company | Legislation enacted |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of facilities | facility |  |  |  |  |  |  |  |  | 11 |  |  |  |  |  |  |  |  |  |
CCR | Virginia Electric and Power Company | Legislation enacted | EPA | Environmental Protection Agency Final Rule Regulating Management of Coal Combustion Residual | Facilities Subject to Coal Combustion Residual Final Rule |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of facilities with CCR | facility |  |  |  |  |  |  |  | 8 |  |  |  |  |  |  |  |  |  |  |
ARO recorded related to future ash pond and landfill closure costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 238,000,000 |  | 386,000,000 |  |
CCR | Virginia Electric and Power Company | Legislation enacted | EPA | Environmental Protection Agency Final Rule Regulating Management of Coal Combustion Residual | Facilities Subject to Coal Combustion Residual Final Rule | Other operations and maintenance expense |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Incremental charge |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 197,000,000 |  | 99,000,000 |  |
CCR | Virginia Electric and Power Company | Legislation enacted | EPA | Environmental Protection Agency Final Rule Regulating Management of Coal Combustion Residual | Facilities Subject to Coal Combustion Residual Final Rule | Other Noncurrent Liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reversal of contingent liability |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 121,000,000 |  |
CCR | Virginia Electric and Power Company | Legislation enacted | EPA | Environmental Protection Agency Final Rule Regulating Management of Coal Combustion Residual | Facilities Subject to Coal Combustion Residual Final Rule | Remediation Property for Sale, Abandonment or Disposal |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in property plant and equipment associated with asset retirement costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 17,000,000 |  | $ 166,000,000 |  |
CCR | Virginia Electric and Power Company | Legislation enacted | EPA | Environmental Protection Agency Final Rule Regulating Management of Coal Combustion Residual | Facilities Subject to Coal Combustion Residual Final Rule | Remediation Property for Sale, Abandonment or Disposal | Asset Retirement Obligation Costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in regulatory assets associated with asset retirement costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 24,000,000 |  |  |  |
CCR | Virginia Electric and Power Company | Legislation enacted | EPA | Administrative Appeals in Circuit Court for City of Richmond | Environmental Protection Agency Final Rule Regulating Management of Coal Combustion Residual | Pending Litigation | Facilities Subject to Coal Combustion Residual Final Rule |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of parties | party |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |
CCR | Virginia Electric and Power Company | Legislation enacted | EPA | Administrative Appeals in Circuit Court for City of Richmond | Environmental Protection Agency Final Rule Regulating Management of Coal Combustion Residual | Settled Litigation | Facilities Subject to Coal Combustion Residual Final Rule |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of parties | party |  |  |  | 1 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
[1] | Primarily reflects AROs assumed in the Dominion Questar Combination. See Note 3 for further information.
[2] | Primarily reflects future ash pond and landfill closure costs at certain utility generation facilities. See Note 22 for further information.

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