Variable Interest Entities (Narrative) (Details) (Virginia Electric and Power Company [Member], USD $)	3 Months Ended
	Mar. 31, 2012 MW	Mar. 31, 2011
Virginia Electric and Power Company [Member]
Long term capacity contract non utility generators	4
Aggregate generation capacity from long-term power and capacity contracts (MW)	870
Contracts expiry date start range	2015
Contracts expiry date end range	2021
Remaining purchase commitments	$ 1,200,000,000
Payment for electric capacity	55,000,000	53,000,000
Payment for electric energy	19,000,000	39,000,000
Shared services purchased	$ 96,000,000	$ 93,000,000