Commitments and Contingencies (Narrative) (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Oct. 31, 2011
CAA authorized daily civil penalties for non compliance	$ 37,500
Estimated costs to install cooling towers	570,000,000
Remaining expenditures to install cooling towers	25,000,000
Percent further emmision reduction goals in participating state power plant CO2 emissions (percentage)	10.00%
Acquisition Cost Of Rggi Allowances	38,000,000
Exposure under guarantees	4,188,000,000
Purchased surety bonds	165,000,000
Authorized issuance of standby letters of credit	36,000,000
Receivables for spent nuclear fuel related costs	122,000,000
Virginia Electric and Power Company
Purchased surety bonds	72,000,000
Authorized issuance of standby letters of credit	15,000,000
Receivables for spent nuclear fuel related costs	88,000,000
Third Party and Equity Method Investee
Issued guarantees	86,000,000
Exposure under guarantees	45,000,000
Minimum
CAA authorized daily civil penalties for non compliance	25,000
Maximum
CAA authorized daily civil penalties for non compliance	37,500
MF Global Bankruptcy
Initial margin posted		73,000,000
Margin received	$ 8,000,000