Investments (Selected Information Regarding Marketable Equity and Debt Securities) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Available-for-sale securities:
Proceeds from sales	$ 1,235		$ 1,476		$ 1,356
Realized gains	171	[1]	157	[1]	98	[1]
Realized losses	30	[1]	33	[1]	33	[1]
Virginia Electric and Power Company
Available-for-sale securities:
Proceeds from sales	549		572		626
Realized gains	73	[1]	52	[1]	42	[1]
Realized losses	$ 12	[1]	$ 14	[1]	$ 11	[1]

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