Commitments and Contingencies (Guarantees, Surety Bonds and Letters of Credit) (Narrative) (Details) $ in Millions	Dec. 31, 2016 USD ($)
Guarantor Obligations [Line Items]
Purchased surety bonds	$ 149
Authorized issuance of standby letters of credit	85
Exposure under guarantees	5,818	[1]
Virginia Electric and Power Company
Guarantor Obligations [Line Items]
Purchased surety bonds	71
Virginia Electric and Power Company | Debt
Guarantor Obligations [Line Items]
Exposure under guarantees	14
Dominion Gas Holdings, LLC
Guarantor Obligations [Line Items]
Purchased surety bonds	22
Third Party and Equity Method Investee
Guarantor Obligations [Line Items]
Estimate of possible loss	$ 48

[1] Excludes Dominion's guarantee for the construction of the new corporate office property discussed further within Lease Commitments above.