Commitments and Contingencies (Narrative) (Details)	1 Months Ended												6 Months Ended	12 Months Ended
	Jul. 31, 2016 party	Jun. 30, 2016 USD ($) facility party site	Apr. 30, 2016 USD ($)	Oct. 31, 2015	Jun. 30, 2015 party	Apr. 30, 2015 facility	Dec. 31, 2014 USD ($)	Oct. 31, 2014 facility	Jun. 30, 2014 unit	Jul. 31, 2013 unit	Sep. 30, 2011 party	Jul. 31, 2011 state group MW	Jun. 30, 2016 USD ($) facility party site	Dec. 31, 2015 USD ($) party
Investments in and Advances to Affiliates [Line Items]
Extension period for MATS compliance			1 year						1 year
Number of coal fired generating units | unit									2
Requested compliance extension under EPA Administrative Order				1 year
Maximum period for consideration of CO2 emissions from biomass projects												3 years
Number of parties issued UAO | party											22
Daily civil penalties for non compliance													$ 37,500
Coal Tar and Other Potentially Harmful Materials
Investments in and Advances to Affiliates [Line Items]
Number of former manufactured gas plant sites | site		17											17
Former Gas Plant Site with Post Closure Groundwater Monitoring Program | Coal Tar and Other Potentially Harmful Materials
Investments in and Advances to Affiliates [Line Items]
Number of former sites | site													1
Dominion Gas Holdings, LLC | Coal Tar and Other Potentially Harmful Materials
Investments in and Advances to Affiliates [Line Items]
Number of former manufactured gas plant sites | site		12											12
Virginia Electric and Power Company
Investments in and Advances to Affiliates [Line Items]
Number of coal fired generating units | unit										3
Virginia Electric and Power Company | Coal Tar and Other Potentially Harmful Materials
Investments in and Advances to Affiliates [Line Items]
Number of former manufactured gas plant sites | site		3											3
Preliminary costs for options under evaluation for site, minimum		$ 1,000,000											$ 1,000,000
Preliminary costs for options under evaluation for site, maximum		$ 22,000,000											$ 22,000,000
Virginia Electric and Power Company | Possum Point Power Station | Other operations and maintenance
Investments in and Advances to Affiliates [Line Items]
Charge as a result of settlement offer							$ 121,000,000
Virginia Electric and Power Company | Facilities Subject to CCR Final Rule | Environmental Protection Agency Final Rule Regulating Management of CCRs | EPA
Investments in and Advances to Affiliates [Line Items]
Number of facilities with CCR | facility						8
Obligations incurred during the period														$ 386,000,000
Virginia Electric and Power Company | Facilities Subject to CCR Final Rule | Environmental Protection Agency Final Rule Regulating Management of CCRs | EPA | Other operations and maintenance
Investments in and Advances to Affiliates [Line Items]
Incremental charge upon recognition of ARO														99,000,000
Virginia Electric and Power Company | Facilities Subject to CCR Final Rule | Environmental Protection Agency Final Rule Regulating Management of CCRs | ARO's | EPA
Investments in and Advances to Affiliates [Line Items]
Increase in property plant and equipment associated with asset retirement costs														166,000,000
Virginia Electric and Power Company | Facilities Subject to CCR Final Rule | Noncurrent Liabilities | Environmental Protection Agency Final Rule Regulating Management of CCRs | EPA
Investments in and Advances to Affiliates [Line Items]
Reduction in other current liabilities														$ 121,000,000
Virginia Electric and Power Company | Pending Litigation | Facilities Subject to CCR Final Rule | Environmental Protection Agency Final Rule Regulating Management of CCRs | EPA | Administrative Appeals in Circuit Court for the City of Richmond
Investments in and Advances to Affiliates [Line Items]
Number of parties | party														2
Virginia Electric and Power Company | Settled Litigation | Facilities Subject to CCR Final Rule | Environmental Protection Agency Final Rule Regulating Management of CCRs | EPA | Administrative Appeals in Circuit Court for the City of Richmond
Investments in and Advances to Affiliates [Line Items]
Number of parties | party		1
CAIR
Investments in and Advances to Affiliates [Line Items]
Number of states under EPA replacement rule | state												28
Emissions of fossil fuel fired electric generating units (MW) | MW												25
Number of groups of affected states | group												2
CWA
Investments in and Advances to Affiliates [Line Items]
Number of facilities that may be subject to final regulations | facility								14
CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category | EPA
Investments in and Advances to Affiliates [Line Items]
Number of facilities that maybe subject to additional wastewater treatment requirements | facility		8											8
CWA | Virginia Electric and Power Company
Investments in and Advances to Affiliates [Line Items]
Number of facilities that may be subject to final regulations | facility								11
Unfavorable Regulatory Action | Dominion Gas Holdings, LLC | Regulations to Reduce Nitrogen Oxide and Volatile Organic Compounds Emissions | Pennsylvania Department of Environmental Protection
Investments in and Advances to Affiliates [Line Items]
Estimated compliance costs			$ 25,000,000
Breach of Contract Lawsuit | DTI | Pending Litigation
Investments in and Advances to Affiliates [Line Items]
Accrued liability for legal matter		$ 6,000,000											$ 6,000,000
Liquefaction Project | Cove Point | Pending Litigation
Investments in and Advances to Affiliates [Line Items]
Number of parties | party													2
Liquefaction Project | Cove Point | Judicial Ruling
Investments in and Advances to Affiliates [Line Items]
Number of parties | party					1
Liquefaction Project | Cove Point | Judicial Ruling | Subsequent Event
Investments in and Advances to Affiliates [Line Items]
Number of parties | party	1