Significant Financing Transactions - (Narrative) (Details) (USD $)	9 Months Ended					9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended					9 Months Ended		9 Months Ended			9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Aug. 31, 2011	Dec. 31, 2010 Virginia Power [Member]	Sep. 30, 2009 Virginia Power [Member]	Sep. 30, 2011 Virginia Power [Member] Solid Waste Disposal Revenue Bonds Series A [Member]	Sep. 30, 2009 Virginia Power [Member] Solid Waste Disposal Revenue Bonds Series A [Member]	Sep. 30, 2011 Loans Payable [Member] Senior Notes 4.45 Percent Due 2021 [Member]	Mar. 31, 2011 Loans Payable [Member] Senior Notes 4.45 Percent Due 2021 [Member]	Sep. 30, 2011 Loans Payable [Member] Senior Notes 1.80 Percent Due 2014 [Member]	Mar. 31, 2011 Loans Payable [Member] Senior Notes 1.80 Percent Due 2014 [Member]	Sep. 30, 2011 Convertible Debt [Member] days	Sep. 30, 2011 Maximum [Member]	Sep. 30, 2011 Minimum [Member]	Sep. 30, 2011 Senior Notes 4 Point 9 Percent Due In 2041 [Member]	Aug. 31, 2011 Senior Notes 4 Point 9 Percent Due In 2041 [Member]	Sep. 30, 2011 Senior Notes 1 Point 95 Percent Due In 2016 [Member]	Aug. 31, 2011 Senior Notes 1 Point 95 Percent Due In 2016 [Member]	Sep. 30, 2011 Massachusetts Development Finance Agency Recovery Zone Facility Bonds Series 2010 A [Member]	Dec. 31, 2010 Massachusetts Development Finance Agency Recovery Zone Facility Bonds Series 2010 A [Member]	Dec. 31, 2010 Solid Waste Disposal Revenue Bonds Series 2010 B [Member]	Sep. 30, 2011 Solid Waste Disposal Revenue Bonds Series A [Member]
Issuance of long-term debt				$ 100,000,000	$ 60,000,000		$ 160,000,000		$ 500,000,000		$ 400,000,000					$ 500,000,000		$ 450,000,000		$ 160,000,000	$ 75,000,000
Debt instrument, interest rate			2.25%					4.45%		1.80%						4.90%		1.95%
Debt maturity	2041					2040		2021		2014					2041		2016
Duration Of Coupon Rate																			5 years			5 years
Contingent convertible senior notes												165,000,000
Conversion rate, shares of common stock per $1,000 principal amount of senior notes												28.8178
Conversion rate, shares of common stock per $1,000 principal amount of senior notes, conversion price												$ 34.70
Principal amount of senior notes												1,000
Common stock, shares issued	1,000,000
Common stock, cash proceeds	37,000,000	66,000,000
Common Stock Expected To Be Repurchased With Tax Savings													700,000,000	600,000,000
Repurchase of common stock	601,000,000	900,000,000
Repurchase of common stock, shares	13,000,000
Conversion share price unmet	$ 46.37
Minimum consecutive trading days												20
Maximum consecutive trading days												30
Debt Conversion, Converted Instrument, Amount												$ 37,000,000