Investments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended								1 Months Ended	12 Months Ended			1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading Securities	Dec. 31, 2011 Categories of Investments, Marketable Securities, Trading Securities	Dec. 31, 2012 Categories of Investments, Cost-method Investments	Dec. 31, 2011 Categories of Investments, Cost-method Investments	Dec. 31, 2012 Blue Racer	Dec. 31, 2012 Blue Racer	Dec. 31, 2011 Blue Racer	Dec. 31, 2010 Blue Racer	Dec. 31, 2012 Other operations and maintenance expense Blue Racer	Dec. 31, 2012 Virginia Electric and Power Company	Dec. 31, 2011 Virginia Electric and Power Company
Gain (Loss) on Investments [Line Items]
Investments held in our rabbi trusts					$ 95	$ 90	$ 14	$ 17
Equity earnings on investments	25	35	42
Company received distribution from Fowler Ridge in connection with non-recourse permanent financing	58	55		60					115	115	0	0
Carrying amount of Company's investments exceeded its shares of underlying equity	30	32
Ownership percentage									50.00%	50.00%
Gain on purchase of business													72
Gain on purchase of business, net of tax													43
Transaction costs on sale													9
Restricted cash and cash equivalent for funding qualifying projects	$ 37	$ 147												$ 10	$ 32