Goodwill and Intangible Assets (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill [Line Items]
Amortization expense for intangible assets	$ 82	$ 78	$ 107
Acquisition of intangible assets	102
Weighted-average amortization period (years)	19 years
Virginia Electric and Power Company
Goodwill [Line Items]
Amortization expense for intangible assets	22	22	26
Acquisition of intangible assets	$ 53
Weighted-average amortization period (years)	31 years