Investments (Selected Information Regarding Marketable Equity and Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Available-for-sale securities:
Proceeds from sales	$ 308		$ 349		$ 862		$ 764
Realized gains	29	[1]	28	[1]	92		56
Realized losses	10	[1]	15	[1]	16		19
Virginia Electric and Power Company
Available-for-sale securities:
Proceeds from sales	135		162		324		353
Realized gains	10	[1]	10	[1]	26	[1]	21	[1]
Realized losses	$ 5	[1]	$ 5	[1]	$ 8	[1]	$ 7	[1]

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