Regulatory Assets and Liabilities (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($)
Public Utilities, General Disclosures [Line Items]
Regulatory assets past expenditures not earning return	$ 299
Period for which expenditures are expected to be recovered	2 years
Virginia Electric and Power Company
Public Utilities, General Disclosures [Line Items]
Regulatory assets past expenditures not earning return	$ 234
Dominion Gas Holdings, LLC
Public Utilities, General Disclosures [Line Items]
Regulatory assets past expenditures not earning return	$ 23