Goodwill and Intangible Assets (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Amortization expense for intangible assets	$ 78	$ 71	$ 72
Acquisition of intangible assets	$ 78
Weighted-average amortization period (years)	8 years
Virginia Electric and Power Company
Goodwill [Line Items]
Amortization expense for intangible assets	$ 25	24	22
Acquisition of intangible assets	$ 34
Weighted-average amortization period (years)	6 years
Dominion Gas Holdings, LLC
Goodwill [Line Items]
Amortization expense for intangible assets	$ 18	$ 17	$ 16
Acquisition of intangible assets	$ 24
Weighted-average amortization period (years)	14 years