Investments (Selected Information Regarding Marketable Equity and Debt Securities) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Available-for-sale securities:
Proceeds from sales		$ 357	$ 838	$ 937	$ 1,524
Realized gains	[1]	65	57	165	120
Realized losses	[1]	40	7	69	20
Virginia Electric and Power Company
Available-for-sale securities:
Proceeds from sales		198	116	407	415
Realized gains	[2]	45	22	82	51
Realized losses	[2]	$ 18	$ 2	$ 33	$ 8

[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.