Investments (Marketable Equity and Debt Securities and Cash Equivalents (Classified as Available-for-sale) and Cost Method Investments in Decommissioning Trust Funds) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Investment Holdings [Line Items]
Total Unrealized Gains	$ 1,408	[1]	$ 1,252	[1]
Total Unrealized Losses	(6)	[1],[2]	(18)	[1],[2]
Nuclear decommissioning trust funds	4,196		3,903
Total Amortized Cost	2,794		2,669
Net assets related to pending sales and purchases of securities	3		11
Fair value of securities in an unrealized loss position	379		604
Virginia Electric and Power Company
Investment Holdings [Line Items]
Total Unrealized Gains	619	[1]	538	[1]
Total Unrealized Losses	(3)	[1],[3]	(9)	[1],[3]
Nuclear decommissioning trust funds	1,930		1,765
Total Amortized Cost	1,314		1,236
Net assets related to pending sales and purchases of securities	6		6
Fair value of securities in an unrealized loss position	170		299
Cost method investments
Investment Holdings [Line Items]
Other investments and securities, at cost	86		106
Total Unrealized Gains	0	[1]	0	[1]
Total Unrealized Losses	0	[1]	0	[1]
Nuclear decommissioning trust funds	86		106
Cost method investments | Virginia Electric and Power Company
Investment Holdings [Line Items]
Other investments and securities, at cost	86		106
Total Unrealized Gains	0	[1]	0	[1]
Total Unrealized Losses	0	[1]	0	[1]
Nuclear decommissioning trust funds	86		106
Cash equivalents and other
Investment Holdings [Line Items]
Other investments and securities, at cost	16	[4]	110	[4]
Total Unrealized Gains	0	[1],[4]	0	[1],[4]
Total Unrealized Losses	0	[1],[4]	0	[1],[4]
Nuclear decommissioning trust funds	16	[4]	110	[4]
Cash equivalents and other | Virginia Electric and Power Company
Investment Holdings [Line Items]
Other investments and securities, at cost	6	[5]	37	[5]
Total Unrealized Gains	0	[1],[5]	0	[1],[5]
Total Unrealized Losses	0	[1],[5]	0	[1],[5]
Nuclear decommissioning trust funds	6	[5]	37	[5]
Corporate debt instruments
Investment Holdings [Line Items]
Amortized Cost	424		332
Total Unrealized Gains	19	[1]	16	[1]
Total Unrealized Losses	(2)	[1]	(3)	[1]
Nuclear decommissioning trust funds	441		345
Corporate debt instruments | Virginia Electric and Power Company
Investment Holdings [Line Items]
Amortized Cost	242		185
Total Unrealized Gains	9	[1]	8	[1]
Total Unrealized Losses	(1)	[1]	(2)	[1]
Nuclear decommissioning trust funds	250		191
U.S. Treasury securities and agency debentures
Investment Holdings [Line Items]
Amortized Cost	597		589
Total Unrealized Gains	13	[1]	8	[1]
Total Unrealized Losses	(4)	[1]	(10)	[1]
Nuclear decommissioning trust funds	606		587
U.S. Treasury securities and agency debentures | Virginia Electric and Power Company
Investment Holdings [Line Items]
Amortized Cost	197		214
Total Unrealized Gains	3	[1]	1	[1]
Total Unrealized Losses	(2)	[1]	(3)	[1]
Nuclear decommissioning trust funds	198		212
State and municipal
Investment Holdings [Line Items]
Amortized Cost	332		297
Total Unrealized Gains	23	[1]	11	[1]
Total Unrealized Losses	0	[1]	(5)	[1]
Nuclear decommissioning trust funds	355		303
State and municipal | Virginia Electric and Power Company
Investment Holdings [Line Items]
Amortized Cost	197		163
Total Unrealized Gains	13	[1]	4	[1]
Total Unrealized Losses	0	[1]	(4)	[1]
Nuclear decommissioning trust funds	210		163
Other securities
Investment Holdings [Line Items]
Amortized Cost	66		3
Total Unrealized Gains	0	[1]	0	[1]
Total Unrealized Losses	0	[1]	0	[1]
Nuclear decommissioning trust funds	66		3
Other securities | Virginia Electric and Power Company
Investment Holdings [Line Items]
Amortized Cost	23
Total Unrealized Gains	0	[1]
Total Unrealized Losses	0	[1]
Nuclear decommissioning trust funds	23
U.S.: | Equity securities: | Large Cap
Investment Holdings [Line Items]
Amortized Cost	1,273		1,183
Total Unrealized Gains	1,353	[1]	1,194	[1]
Total Unrealized Losses	0	[1]	0	[1]
Nuclear decommissioning trust funds	2,626		2,377
U.S.: | Equity securities: | Large Cap | Virginia Electric and Power Company
Investment Holdings [Line Items]
Amortized Cost	563		506
Total Unrealized Gains	594	[1]	514	[1]
Total Unrealized Losses	0	[1]	0	[1]
Nuclear decommissioning trust funds	1,157		1,020
U.S.: | Equity securities: | Other
Investment Holdings [Line Items]
Amortized Cost			49
Total Unrealized Gains			23	[1]
Total Unrealized Losses			0	[1]
Nuclear decommissioning trust funds			72
U.S.: | Equity securities: | Other | Virginia Electric and Power Company
Investment Holdings [Line Items]
Amortized Cost			25
Total Unrealized Gains			11	[1]
Total Unrealized Losses			0	[1]
Nuclear decommissioning trust funds			$ 36

[1] Included in AOCI and the nuclear decommissioning trust regulatory liability as discussed in Note 2.

[2] The fair value of securities in an unrealized loss position was $379 million and $604 million at December 31, 2014 and 2013, respectively.

[3] The fair value of securities in an unrealized loss position was $170 million and $299 million at December 31, 2014 and 2013, respectively.

[4] Includes pending sales of securities of $3 million and $11 million at December 31, 2014 and 2013, respectively.

[5] Includes pending sales of securities of $6 million at December 31, 2014 and 2013.