Investments (Selected Information Regarding Marketable Equity and Debt Securities) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Available-for-sale securities:
Proceeds from sales		$ 1,340	$ 1,235	$ 1,476
Realized gains	[1]	219	171	157
Realized losses	[1]	84	30	33
Virginia Electric and Power Company
Available-for-sale securities:
Proceeds from sales		639	549	572
Realized gains	[2]	110	73	52
Realized losses	[2]	$ 43	$ 12	$ 14

[1] Includes realized gains and losses recorded to the nuclear decommissioning trust regulatory liability as discussed in Note 2.

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