Investments (Selected Information Regarding Marketable Equity and Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Available-for-sale securities:
Proceeds from sales	$ 244		$ 308		$ 686		$ 862
Realized gains	25	[1]	29	[1]	63	[1]	92	[1]
Realized losses	7	[1]	10	[1]	13	[1]	16	[1]
Virginia Electric and Power Company
Available-for-sale securities:
Proceeds from sales	95		135		299		324
Realized gains	10	[1]	10	[1]	29	[1]	26	[1]
Realized losses	$ 3	[1]	$ 5	[1]	$ 6	[1]	$ 8	[1]

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