Variable Interest Entities (Narrative) (Details) (Virginia Electric and Power Company, USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 generator MW	Sep. 30, 2011
Long term capacity contract non utility generators (generators)			4
Aggregate generation capacity from long-term power and capacity contracts (MW)			870
Remaining purchase commitments			$ 1,100,000,000
Payment for electric capacity	52,000,000	52,000,000	160,000,000	156,000,000
Payment for electric energy	27,000,000	38,000,000	62,000,000	103,000,000
Shared services purchased	$ 86,000,000	$ 100,000,000	$ 238,000,000	$ 292,000,000
Minimum
Contracts expiry date start range			2015
Maximum
Contracts expiry date start range			2021