Acquisitions and Dispositions (Narrative) (Details)				1 Months Ended							6 Months Ended		12 Months Ended
		Jan. 31, 2016 USD ($) $ / shares	Apr. 01, 2015 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) Project MW	Sep. 30, 2015 USD ($) Project mi MW shares	Jun. 30, 2015 USD ($) Project MW	Jan. 31, 2015 USD ($) mi	Mar. 31, 2014 USD ($)	Aug. 31, 2013 USD ($)	Jun. 30, 2013 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2013 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining ownership interest percentage				100.00%							100.00%		100.00%
Required payments				$ 50,000,000							$ 50,000,000		$ 50,000,000
Contributions from SunEdison to Four Brothers and Three Cedars													103,000,000
Goodwill	[1]			$ 3,294,000,000							$ 3,294,000,000		3,294,000,000	$ 3,044,000,000	$ 3,086,000,000
Proceeds from sale of electric retail energy marketing business													$ 0	187,000,000	0
Asset disposition adjustment														42,000,000
Iroquois
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership percentage	[2]			50.65%							50.65%		50.65%
Elwood
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership percentage									50.00%
Discontinued Operations, Disposed of by Sale | Elwood
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of equity method investment									$ 465,000,000
Discontinued Operations, Disposed of by Sale | Other Income | Elwood
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of investment									35,000,000
After tax gain on sale of investment									$ 25,000,000
Merchant Solar Projects | SunEdison | Call Option
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining ownership interest percentage				67.00%							67.00%		67.00%
Merchant Solar Projects | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
SunEdison's ownership interest in merchant solar projects				33.00%	33.00%						33.00%		33.00%
Number of currently wholly-owned merchant solar projects | Project					24
MW Capacity | MW					425
Sales price of equity interest to noncontrolling interest owners					$ 300,000,000
Number of solar projects sold under agreement | Project				15
Sales price				$ 184,000,000							$ 184,000,000		$ 184,000,000
Electric Retail Energy Marketing Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of electric retail energy marketing business								$ 187,000,000
Gain on sale								100,000,000
After-tax gain on sale								57,000,000
Asset disposition adjustment								$ 31,000,000
Illinois Gas Contracts | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales price										$ 32,000,000		$ 32,000,000
Gain on sale										29,000,000
After-tax gain on sale										18,000,000
Asset disposition adjustment										$ 3,000,000
Brayton Point and Kincaid | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge												48,000,000
Long-lived assets impairment charges, net of tax												$ 28,000,000
Brayton Point and Kincaid | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operation															17,000,000
Loss on discontinued operation, net of tax															18,000,000
Brayton Point and Kincaid | Discontinued Operations, Disposed of by Sale | Loss from Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset disposition adjustment															16,000,000
Partnership Interest | National Grid | Iroquois
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest percentage					20.40%
Partnership Interest | NJNR Pipeline Company | Iroquois
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest percentage					5.53%
Four Brothers Solar, LLC and Three Cedars
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining ownership interest percentage				50.00%							50.00%		50.00%
Four Brothers Solar, LLC and Three Cedars | Investment Credits | Federal
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of expected federal investment tax credits on projects to be claimed				99.00%							99.00%		99.00%
Four Brothers Solar, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase price						$ 64,000,000
Acquisition price payable						$ 62,000,000
MW Capacity | MW						320
Percentage of equity interests acquired						50.00%
Acquisition price in cash						$ 2,000,000
Number of Projects | Project						4
Estimated project cost once constructed				$ 730,000,000							$ 730,000,000		$ 730,000,000
Purchase price						$ 64,000,000
Net property plant and equipment acquired						89,000,000
Amount of noncontrolling interest						25,000,000
Four Brothers Solar, LLC | Obligation to Contribute Capital to Fund Construction of Projects | Limited Liability Company
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Required payments						$ 445,000,000
Amount of contributions				138,000,000							138,000,000		138,000,000
Four Brothers Solar, LLC | Current Liabilities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payable included in other current liabilities				43,000,000							43,000,000		43,000,000
Three Cedars
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase price					$ 43,000,000
Acquisition price payable					$ 37,000,000
MW Capacity | MW					210
Percentage of equity interests acquired					50.00%
Acquisition price in cash					$ 6,000,000
Number of Projects | Project					3
Estimated project cost once constructed				425,000,000							425,000,000		425,000,000
Purchase price					$ 43,000,000
Net property plant and equipment acquired					65,000,000
Amount of noncontrolling interest					22,000,000
Three Cedars | Obligation to Contribute Capital to Fund Construction of Projects | Affiliated Entity
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Required payments					$ 276,000,000
Amount of contributions				60,000,000							60,000,000		60,000,000
Three Cedars | Current Liabilities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payable included in other current liabilities				$ 29,000,000							29,000,000		$ 29,000,000
DCG
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase price							$ 497,000,000
Percentage of equity interests acquired							100.00%
Net property plant and equipment acquired							$ 277,000,000
Length of FERC regulated interstate natural gas pipeline | mi							1,500
Goodwill							$ 250,000,000
Amount expected to be deductible for tax purposes							225,000,000
Amount of regulatory liabilities							$ 38,000,000
SunEdison | Four Brothers Solar, LLC and Three Cedars
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contributions from SunEdison to Four Brothers and Three Cedars											$ 103,000,000
Dominion Midstream Partners, LP | Iroquois
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership percentage	[2]			25.93%							25.93%		25.93%
Dominion Midstream Partners, LP | Partnership Interest | Iroquois
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
SunEdison's ownership interest in merchant solar projects				25.93%							25.93%		25.93%
Ownership percentage					25.93%
Length of FERC regulated interstate natural gas pipeline | mi					416
Number of common units issued | shares					8,600,000
Value of common units at closing					$ 216,000,000
Dominion Midstream Partners, LP | Partnership Interest | National Grid | Iroquois
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of common units issued | shares					6,800,000
Dominion Midstream Partners, LP | Partnership Interest | NJNR Pipeline Company | Iroquois
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of common units issued | shares					1,800,000
Dominion Midstream Partners, LP | Affiliated Entity | DCG | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales price			$ 501,000,000
Ownership interest percentage			100.00%
Dominion Midstream Partners, LP | Affiliated Entity | DCG | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Unsecured Promissory Note Receivable | Notes Receivable
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Term of senior unsecured promissory note payable			2 years
Senior unsecured promissory note payable by Dominion Midstream			$ 301,000,000
Interest rate (percentage)			0.60%
Dominion Midstream Partners, LP | Affiliated Entity | Partnership Interest | DCG | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of common units issued | shares			5,112,139
Value of common units at closing			$ 200,000,000
Number of trading days			10 days
Price per unit | $ / shares			$ 39.12
Dominion Gas Holdings, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill	[1]			$ 542,000,000							$ 542,000,000		$ 542,000,000	542,000,000	$ 545,000,000
Asset disposition adjustment														$ 3,000,000
Dominion Gas Holdings, LLC | Iroquois
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership percentage	[2]			24.72%							24.72%		24.72%
Dominion Gas Holdings, LLC | Partnership Interest | Iroquois
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership percentage				24.72%							24.72%		24.72%
Virginia Electric and Power Company | Morgans Corner Solar Energy, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Purchase price				$ 47,000,000
MW Capacity | MW				20
Percentage of equity interests acquired				100.00%							100.00%		100.00%
Virginia Electric and Power Company | Morgans Corner Solar Energy, LLC | Solar Development Project
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total cost of project placed into service				$ 49,000,000							$ 49,000,000		$ 49,000,000
Virginia Electric and Power Company | Morgans Corner Solar Energy, LLC | Supply Agreement with US Navy
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Duration of supply agreement				10 years
Subsequent Event | Questar Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Price per unit | $ / shares		$ 25
Purchase price		$ 4,400,000,000
Debt outstanding		1,600,000,000
Acquisition price payable		3,900,000,000
Required termination fee to Questar per agreement		154,000,000
Required termination fee to Dominion per agreement		$ 99,000,000

[1] Goodwill amounts do not contain any accumulated impairment losses.

[2] Comprised of Dominion Midstream's interest of 25.93% and Dominion Gas' interest of 24.72%. See Note 15 for more information.