Investments (Selected Information Regarding Marketable Equity and Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Available-for-sale securities:
Proceeds from sales	$ 349		$ 437		$ 764		$ 939
Realized gains	28	[1]	18	[1]	56	[1]	32	[1]
Realized losses	15	[1]	12	[1]	19	[1]	20	[1]
Virginia Electric and Power Company
Available-for-sale securities:
Proceeds from sales	162		253		353		596
Realized gains	10	[1]	6	[1]	21	[1]	11	[1]
Realized losses	$ 5	[1]	$ 4	[1]	$ 7	[1]	$ 8	[1]

[1] Includes realized gains or losses recorded to the decommissioning trust regulatory liability.