Goodwill and Intangible Assets (Components of Intangible Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 864	$ 968
Accumulated Amortization	328	(331)
Virginia Electric and Power Company
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	303	285
Accumulated Amortization	122	(102)
Software, licenses and other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	859	888
Accumulated Amortization	327	(278)
Software, licenses and other | Virginia Electric and Power Company
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	303	285
Accumulated Amortization	122	(102)
Emissions allowances
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5	80
Accumulated Amortization	$ 1	$ (53)