Investments (Selected Information Regarding Marketable Equity and Debt Securities) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Available-for-sale securities:
Proceeds from sales		$ 368	$ 337
Realized gains	[1]	25	56
Realized losses	[1]	19	17
Virginia Electric and Power Company
Available-for-sale securities:
Proceeds from sales		193	133
Realized gains	[2]	12	18
Realized losses	[2]	$ 10	$ 11

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

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