Investments (Narrative) (Details) (USD $)	1 Months Ended			3 Months Ended					9 Months Ended			1 Months Ended	3 Months Ended		1 Months Ended
	Jan. 31, 2014 Blue Racer	Mar. 31, 2014 Blue Racer Pipelines	Mar. 31, 2013 Blue Racer Pipelines	Sep. 30, 2013 Blue Racer Pipelines	Sep. 30, 2014 Categories of Investments, Marketable Securities, Trading Securities	Dec. 31, 2013 Categories of Investments, Marketable Securities, Trading Securities	Sep. 30, 2014 Cost method investments	Dec. 31, 2013 Cost method investments	Sep. 30, 2014 Dominion Gas Holdings, LLC	Sep. 30, 2013 Dominion Gas Holdings, LLC	Dec. 31, 2013 Dominion Gas Holdings, LLC	Mar. 31, 2014 Dominion Gas Holdings, LLC Blue Racer Pipelines	Sep. 30, 2013 Dominion Gas Holdings, LLC Blue Racer Pipelines	Sep. 30, 2013 Dominion Gas Holdings, LLC Blue Racer Pipelines Other Operations And Maintenance Expense	Sep. 30, 2014 Gas Distribution Atlantic Coast Pipeline Jointly Owned Natural Gas Pipeline Pipelines mi Member	Sep. 30, 2014 Gas Distribution Atlantic Coast Pipeline Jointly Owned Natural Gas Pipeline Minimum Pipelines	Sep. 30, 2014 Gas Distribution Atlantic Coast Pipeline Jointly Owned Natural Gas Pipeline Maximum Pipelines	Sep. 30, 2014 Gas Distribution Atlantic Coast Pipeline Duke Energy Corporation Jointly Owned Natural Gas Pipeline Pipelines	Sep. 30, 2014 Gas Distribution Atlantic Coast Pipeline Piedmont Natural Gas Company Jointly Owned Natural Gas Pipeline Pipelines	Sep. 30, 2014 Gas Distribution Atlantic Coast Pipeline AGL Resources Inc Jointly Owned Natural Gas Pipeline Pipelines
Gain (Loss) on Investments [Line Items]
Assets Held-in-trust					$ 109,000,000	$ 107,000,000	$ 7,000,000	$ 10,000,000
Equity in earnings on investments									17,000,000	16,000,000
Distributions received from investment									10,000,000	12,000,000
Carrying amount of investment that exceeded share of underlying equity									9,000,000		8,000,000
Initial membership interests in pipeline															45.00%			40.00%	10.00%	5.00%
Length of natural gas pipeline															550
Estimated cost to construct pipeline																4,500,000,000	5,000,000,000
Number of members															4
Duration of contract for customers of pipeline															20 years
Cash proceeds from sale of assets		84,000,000	47,000,000									17,000,000	83,000,000
Gain on sale of assets			25,000,000									59,000,000		75,000,000
After tax gain on sale of assets		34,000,000	14,000,000									35,000,000		42,000,000
Extinguishment of affiliated current borrowings												67,000,000
Write off of goodwill	6,000,000		2,000,000									3,000,000
Increase in equity method investment	155,000,000			473,000,000
Consideration for Northern System		$ 84,000,000