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, 2012		Dec. 31, 2011
Investment Holdings [Line Items]
Total amortized cost basis	$ 2,511		$ 2,390
Total Unrealized Gains	821	[1]	611	[1]
Total Unrealized Losses	(2)	[1],[2]	(2)	[1],[2]
Fair Value	3,330		2,999
Net assets related to pending sales and purchases of securities	6		11
Fair value of securities in an unrealized loss position	195		164
Cost method investments
Investment Holdings [Line Items]
Other investments and securities, at cost	117		118
Total Unrealized Gains	0	[1]	0	[1]
Total Unrealized Losses	0	[1]	0	[1]
Fair Value	117		118
Cash equivalents and other
Investment Holdings [Line Items]
Other investments and securities, at cost	72	[3]	46	[3]
Total Unrealized Gains	0	[1],[3]	0	[1],[3]
Total Unrealized Losses	0	[1],[3]	0	[1],[3]
Fair Value	72	[3]	46	[3]
Equity securities: | Large Cap | U.S.:
Investment Holdings [Line Items]
Amortized Cost	1,210		1,152
Total Unrealized Gains	732	[1]	537	[1]
Total Unrealized Losses	0	[1]	0	[1]
Fair Value	1,942		1,689
Equity securities: | Other | U.S.:
Investment Holdings [Line Items]
Amortized Cost	40		36
Total Unrealized Gains	13	[1]	10	[1]
Total Unrealized Losses	0	[1]	0	[1]
Fair Value	53		46
Corporate debt instruments
Investment Holdings [Line Items]
Amortized Cost	295		314
Total Unrealized Gains	30	[1]	19	[1]
Total Unrealized Losses	0	[1]	(1)	[1]
Fair Value	325		332
U.S. Treasury securities and agency debentures
Investment Holdings [Line Items]
Amortized Cost	523		437
Total Unrealized Gains	19	[1]	20	[1]
Total Unrealized Losses	(2)	[1]	(1)	[1]
Fair Value	540		456
State and municipal
Investment Holdings [Line Items]
Amortized Cost	248		264
Total Unrealized Gains	26	[1]	24	[1]
Total Unrealized Losses	0	[1]	0	[1]
Fair Value	274		288
Other
Investment Holdings [Line Items]
Amortized Cost	6		23
Total Unrealized Gains	1	[1]	1	[1]
Total Unrealized Losses	0	[1]	0	[1]
Fair Value	7		24
Virginia Electric and Power Company
Investment Holdings [Line Items]
Total amortized cost basis	1,179		1,123
Total Unrealized Gains	337	[1]	249	[1]
Total Unrealized Losses	(1)	[1],[4]	(2)	[1],[4]
Fair Value	1,515		1,370
Net assets related to pending sales and purchases of securities	6		13
Fair value of securities in an unrealized loss position	104		99
Virginia Electric and Power Company | Cost method investments
Investment Holdings [Line Items]
Other investments and securities, at cost	117		118
Total Unrealized Gains	0	[1]	0	[1]
Total Unrealized Losses	0	[1]	0	[1]
Fair Value	117		118
Virginia Electric and Power Company | Cash equivalents and other
Investment Holdings [Line Items]
Other investments and securities, at cost	44	[5]	27	[5]
Total Unrealized Gains	0	[1],[5]	0	[1],[5]
Total Unrealized Losses	0	[1],[5]	0	[1],[5]
Fair Value	44	[5]	27	[5]
Virginia Electric and Power Company | Equity securities: | Large Cap | U.S.:
Investment Holdings [Line Items]
Amortized Cost	481		460
Total Unrealized Gains	298	[1]	218	[1]
Total Unrealized Losses	0	[1]	0	[1]
Fair Value	779		678
Virginia Electric and Power Company | Equity securities: | Other | U.S.:
Investment Holdings [Line Items]
Amortized Cost	20		18
Total Unrealized Gains	7	[1]	5	[1]
Total Unrealized Losses	0	[1]	0	[1]
Fair Value	27		23
Virginia Electric and Power Company | Corporate debt instruments
Investment Holdings [Line Items]
Amortized Cost	179		204
Total Unrealized Gains	17	[1]	11	[1]
Total Unrealized Losses	0	[1]	(1)	[1]
Fair Value	196		214
Virginia Electric and Power Company | U.S. Treasury securities and agency debentures
Investment Holdings [Line Items]
Amortized Cost	231		166
Total Unrealized Gains	4	[1]	4	[1]
Total Unrealized Losses	(1)	[1]	0	[1]
Fair Value	234		170
Virginia Electric and Power Company | State and municipal
Investment Holdings [Line Items]
Amortized Cost	106		114
Total Unrealized Gains	11	[1]	10	[1]
Total Unrealized Losses	0	[1]	0	[1]
Fair Value	117		124
Virginia Electric and Power Company | Other
Investment Holdings [Line Items]
Amortized Cost	1		16
Total Unrealized Gains	0	[1]	1	[1]
Total Unrealized Losses	0	[1]	(1)	[1]
Fair Value	$ 1		$ 16

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

[2] The fair value of securities in an unrealized loss position was $195 million and $164 million at December 31, 2012 and 2011, respectively.

[3] Includes pending purchases of securities of $6 million and $11 million at December 31, 2012 and 2011, respectively.

[4] The fair value of securities in an unrealized loss position was $104 million and $99 million at December 31, 2012 and 2011, respectively.

[5] Includes pending sales of securities of $6 million and pending purchases of securities of $13 million at December 31, 2012 and 2011, respectively