Commitments and Contingencies (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended												1 Months Ended	3 Months Ended
	Sep. 30, 2011 Party	Mar. 31, 2013 Site	Mar. 31, 2013 Virginia Electric and Power Company Site	Mar. 31, 2013 Third Party and Equity Method Investee	Mar. 31, 2013 Minimum	Mar. 31, 2013 Maximum	Mar. 31, 2013 Through 2019 Third Party and Equity Method Investee	Mar. 31, 2013 Other		Apr. 25, 2013 Other Guarantee One Subsequent Event		Apr. 25, 2013 Other Guarantee Two Subsequent Event		Jul. 31, 2011 CAA Group MW State	Mar. 31, 2013 CAA	Apr. 25, 2013 CAA Subsequent Event
Number of states under EPA replacement rule														28
Emissions of fossil fuel fired electric generating units (MW)														25
Number of groups of affected states														2
Amount of civil penalty				$ 89,000,000											$ 13,000,000	$ 3,000,000
Amount to fund environmental mitigation projects																10,000,000
Period for public comment (days)															30 days
Number of parties issued UAO	22
Daily civil penalties for non compliance		37,500
Number of former manufactured gas plant sites		17	3
Percent further emmision reduction goals in participating state power plant CO2 emissions (percentage)		10.00%
Exposure under guarantees		4,252,000,000		59,000,000			98,000,000	638,000,000	[1]	150,000,000	[1]	1,750,000,000	[1]
Annual future contributions					4,000,000	19,000,000
Guarantee arrangements to facilitate liquefaction project annual guarantee (cannot exceed $175 million annually)												175,000,000	[1]
Purchased surety bonds		150,000,000	56,000,000
Authorized issuance of standby letters of credit		$ 19,000,000	$ 2,000,000

[1] Guarantees related to other miscellaneous contractual obligations such as leases, environmental obligations and construction projects. Also includes guarantees related to certain DEI subsidiaries' obligations for equity capital contributions and energy generation associated with Fowler Ridge and NedPower.