Acquisitions and Dispositions (Narrative) (Details) $ / shares in Units, a in Thousands, $ in Millions		1 Months Ended												3 Months Ended		9 Months Ended		15 Months Ended
	Apr. 01, 2015 USD ($) $ / shares shares	Sep. 30, 2016 USD ($) MW	Aug. 31, 2016 USD ($) project MW	Jul. 31, 2016 USD ($) a	Apr. 30, 2016 USD ($) a	Jan. 31, 2016 USD ($) a	Dec. 31, 2015 USD ($) project		Sep. 30, 2015 USD ($) a field project MW	Jun. 30, 2015 USD ($) project	Mar. 31, 2015 USD ($) a field	Jan. 31, 2015 USD ($) mi	Dec. 31, 2013 USD ($) a field	Dec. 31, 2017 USD ($)	Sep. 30, 2016 USD ($) MW	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($) a field project	Sep. 30, 2016 USD ($)	Nov. 30, 2016	Nov. 30, 2014 a field
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cost of project																$ 21	$ 278
Contributions from SunEdison to Four Brothers and Three Cedars																178
Goodwill		$ 6,405					$ 3,294	[1]							$ 6,405	$ 6,405		$ 6,405
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]
MW Capacity | MW									425
Percentage of equity interest sold to noncontrolling interest owners		33.00%							33.00%						33.00%	33.00%	33.00%	33.00%
Number of solar projects | project									24								24
Total number of solar projects related to potential sale | project							15
Amount of consideration (up to $200 million for assignment of shale development rights)						$ 117	$ 184
Dominion Gas Holdings, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill		$ 542					$ 542	[2]							$ 542	$ 542		$ 542
Dominion Gas Holdings, LLC | Marcellus Shale | Shale development rights
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount of consideration (up to $200 million for assignment of shale development rights)				$ 5		$ 5					$ 27		$ 200
Development rights (number of acres) | a				2		2					11		79							24
Number of natural gas storage fields | field											1		1							1
Duration of conveyance of rights													9 years
Dominion Gas Holdings, LLC | Marcellus Shale | Shale development rights | Other operations and maintenance
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of assets				$ 5		$ 5					$ 27
After tax gain on sale of assets				$ 3		$ 3					$ 16
Dominion Gas Holdings, LLC | Marcellus Shale | Shale development rights | Amended Agreement to Extend Conveyance of Development Rights
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Development rights (number of acres) | a					70						9
Duration of conveyance of rights											2 years
Partial interest in remaining acres conveyed (percentage)					32.00%
Dominion Gas Holdings, LLC | Marcellus Shale | Shale development rights | Amended Agreement to Extend Conveyance of Development Rights | Other operations and maintenance
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deferred revenue recognized from conveyance of rights					$ 35						$ 43
Deferred revenue recognized from conveyance of rights, after tax					$ 21						$ 27
Dominion Gas Holdings, LLC | Utica and Point Pleasant Shale | Shale development rights
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount of consideration (up to $200 million for assignment of shale development rights)									$ 52								$ 52
Development rights (number of acres) | a									16								16
Number of natural gas storage fields | field									1								1
Proceeds received with conveyance of acreage									$ 52
Dominion Gas Holdings, LLC | Utica and Point Pleasant Shale | Shale development rights | Other operations and maintenance
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of assets									52
After tax gain on sale of assets									29
Terra Nova Renewable Partners | Call Option | Merchant Solar Projects
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage ownership in total units		67.00%													67.00%	67.00%		67.00%
Dominion Midstream Partners, LP | DCG | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Affiliate
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount of consideration (up to $200 million for assignment of shale development rights)	$ 501
Percentage of equity interests contributed	100.00%
Dominion Midstream Partners, LP | DCG | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Affiliate | Partnership Interest
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 issued	$ 200
Number of trading days used to determine weighted average trading price	10 days
Dominion Midstream Partners, LP | DCG | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Affiliate | Partnership Interest | Weighted Average
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Price per unit | $ / shares	$ 39.12
Dominion Midstream Partners, LP | DCG | Disposal Group, Disposed of by Sale, Not Discontinued Operations | Affiliate | Senior unsecured promissory note payable by Dominion Midstream | Unsecured Promissory Note Receivable
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Term of senior unsecured promissory note payable to Dominion	2 years
Amount of senior unsecured promissory note payable to Dominion	$ 301
Annual interest rate percentage for senior unsecured promissory note payable to Dominion	0.60%
Four Brothers and Three Cedars
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage ownership in total units		50.00%													50.00%	50.00%		50.00%
Four Brothers and Three Cedars | SunEdison, Inc
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contributions from SunEdison to Four Brothers and Three Cedars																		$ 281
Four Brothers and Three Cedars | Federal | Investment Tax Credits
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%		99.00%
Four Brothers and Three Cedars | Scenario, Forecast | Subsequent Event | NRG
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of equity interests acquired																			50.00%
Four Brothers
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Acquisition price										$ 64
Liabilities incurred										$ 62
Cost of project															$ 670
Percentage of equity interests acquired										50.00%
Acquisition price in cash										$ 2
Purchase price										64
Net property, plant and equipment acquired										89
Non-controlling interest										$ 25
Number of Projects | project										4
MW Capacity | MW															320
Four Brothers | Other Current Liabilities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payable at period end		$ 7													$ 7	$ 7		$ 7
Three Cedars
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Acquisition price									43
Liabilities incurred									$ 37
Cost of project															$ 450
Percentage of equity interests acquired									50.00%								50.00%
Acquisition price in cash									$ 6
Purchase price									43								$ 43
Net property, plant and equipment acquired									65								65
Non-controlling interest									$ 22								$ 22
Number of Projects | project									3
MW Capacity | MW															210
Three Cedars | Other Current Liabilities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payable at period end		$ 4													$ 4	$ 4		$ 4
Solar Frontier Americas Holding, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Acquisition price			$ 128
Percentage of equity interests acquired			100.00%
Number of Projects | project			2
MW Capacity | MW			50
Solar Frontier Americas Holding, LLC | Scenario, Forecast
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cost of project														$ 130
Virginia Solar, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of equity interests acquired			100.00%
Number of Projects | project			4
MW Capacity | MW			80
Virginia Solar, LLC | Scenario, Forecast
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cost of project														160
Community Energy Solar, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of equity interests acquired		100.00%													100.00%	100.00%		100.00%
MW Capacity | MW		100
Community Energy Solar, LLC | Scenario, Forecast
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cost of project														$ 210
DCG
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Acquisition price												$ 497
Percentage of equity interests acquired												100.00%
Net property, plant and equipment acquired												$ 277
Length of natural gas pipeline (in miles) (nearly 1,500 miles) | mi												1,500
Goodwill												$ 250
Goodwill expected to be deductible for income tax purposes												225
Regulatory liabilities assumed												$ 38

[1] Dominion’s Consolidated Balance Sheet at December 31, 2015 has been derived from the audited Consolidated Financial Statements at that date.

[2] Dominion Gas’ Consolidated Balance Sheet at December 31, 2015 has been derived from the audited Consolidated Financial Statements at that date.