Variable Interest Entities (Narrative) (Details) (Virginia Electric and Power Company, USD $)	3 Months Ended
	Mar. 31, 2013 MW generator	Mar. 31, 2012
Long term capacity contract non utility generators (generators)	4
Aggregate generation capacity from long-term power and capacity contracts (MW)	870
Remaining purchase commitments	$ 1,000,000,000
Payment for electric capacity	55,000,000
Payment for electric energy	20,000,000	19,000,000
Shared services purchased	$ 77,000,000	$ 96,000,000
Minimum
Contracts expiry date start range	2015
Maximum
Contracts expiry date start range	2021