Investments (Selected Information Regarding Marketable Equity and Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Available-for-sale securities:
Proceeds from sales	$ 838		$ 398		$ 1,524		$ 1,260
Realized gains	57	[1]	29	[1]	120	[1]	121	[1]
Realized losses	7	[1]	13	[1]	20	[1]	29	[1]
Virginia Electric and Power Company
Available-for-sale securities:
Proceeds from sales	116		140		415		464
Realized gains	22	[1]	8	[1]	51	[1]	34	[1]
Realized losses	$ 2	[1]	$ 5	[1]	$ 8	[1]	$ 13	[1]

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