Investments (Selected Information Regarding Marketable Equity and Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Available-for-sale securities:
Proceeds from sales	$ 442		$ 554
Realized gains	38	[1]	63	[1]
Realized losses	6	[1]	6	[1]
Virginia Electric and Power Company
Available-for-sale securities:
Proceeds from sales	204		189
Realized gains	19	[1]	16	[1]
Realized losses	$ 3	[1]	$ 3	[1]

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