Variable Interest Entities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended		1 Months Ended	110 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Aug. 31, 2013 Juniper	Aug. 31, 2013 Juniper	Oct. 31, 2011 Juniper	Sep. 30, 2013 Virginia Electric and Power Company	Sep. 30, 2012 Virginia Electric and Power Company	Sep. 30, 2013 Virginia Electric and Power Company MW generator	Sep. 30, 2012 Virginia Electric and Power Company	Sep. 30, 2013 Virginia Electric and Power Company Minimum	Sep. 30, 2013 Virginia Electric and Power Company Maximum
Variable Interest Entities [Line Items]
Long term capacity contract non utility generators (generators)								4
Aggregate generation capacity from long-term power and capacity contracts (MW)								870
Contracts expiry date start range										2015	2021
Remaining purchase commitments								$ 920
Payment for electric capacity						53	52	161	160
Payment for electric energy						29	27	74	62
Shared services purchased						88	86	248	238
Annual lease payments				53
Fair value of property plant and equipment					957
Fair value of debt					896
Fair value of noncontrolling interest					61
Acquisition of Juniper noncontrolling interest	$ 923	$ 0	$ 923