Commitments and Contingencies (Lease Commitments) (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Rental expense		$ 104	$ 99	$ 92
Corporate Office Property | Agreement with Lessor to Construct and Lease Corporate Office Property
Loss Contingencies [Line Items]
Requested cash draws from lessor to fund project costs		46
Required percentage payment of funded amount under certain events of default	89.90%
Required percentage payment for specific full recourse events	100.00%
Lease term	5 years
Extension term of lease	5 years
Required percentage payment to lessor for difference between project costs and sales proceeds	87.00%
Virginia Electric and Power Company
Loss Contingencies [Line Items]
Rental expense		52	51	43
Dominion Gas Holdings, LLC
Loss Contingencies [Line Items]
Rental expense		$ 37	$ 37	$ 35
Lessor | Corporate Office Property | Agreement with Lessor to Construct and Lease Corporate Office Property
Loss Contingencies [Line Items]
Amount of financing commitments to fund estimated project costs	$ 365