Acquisitions and Dispositions (Narrative) (Details) $ / shares in Units, a in Thousands				1 Months Ended									3 Months Ended	9 Months Ended
	Dec. 31, 2016 USD ($) $ / shares	Jan. 31, 2016 USD ($) a	Apr. 01, 2015 USD ($) $ / shares shares	Apr. 30, 2016 USD ($) a	Jan. 31, 2016 USD ($) a	Dec. 31, 2015 USD ($) Project		Sep. 30, 2015 USD ($) Project MW	Jun. 30, 2015 USD ($) Project MW	Mar. 31, 2015 USD ($) a Field	Jan. 31, 2015 USD ($) mi	Dec. 31, 2013 USD ($) a Field	Mar. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Nov. 30, 2014 a Field
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contributions from SunEdison to Four Brothers and Three Cedars													$ 94,000,000
Goodwill						$ 3,294,000,000	[1]						$ 3,294,000,000	$ 3,294,000,000
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]
Percentage of equity interest sold to noncontrolling interest owners								33.00%					33.00%	33.00%
Number of solar projects | Project								24
Expected generation capacity of facilities (mw) | MW								425
Total number of solar projects related to potential sale | Project						15
Amount of consideration		$ 117,000,000			$ 117,000,000	$ 184,000,000
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			$ 501,000,000
Percentage of equity interests			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			$ 200,000,000
Number of trading days used to determine weighted average trading price			10 days
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			$ 301,000,000
Annual interest rate for senior unsecured promissory note payable to Dominion			0.60%
Dominion Gas Holdings, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill						$ 542,000,000	[2]						$ 542,000,000	$ 542,000,000
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		$ 5,000,000			$ 5,000,000					$ 27,000,000		$ 200,000,000
Acres of rights conveyed | 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 | Operations and Maintenance Expense
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of assets					$ 5,000,000					$ 27,000,000
After tax gain on sale of assets					$ 3,000,000					$ 16,000,000
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]
Acres of rights conveyed | a										9
Duration of conveyance of rights										2 years
Deferred revenue													$ 36,000,000	$ 36,000,000
Dominion Gas Holdings, LLC | Marcellus Shale | Shale development rights | Amended Agreement to Extend Conveyance of Development Rights | Operations and Maintenance Expense
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deferred revenue recognized from conveyance of rights										$ 43,000,000
Deferred revenue recognized from conveyance of rights, after tax										$ 27,000,000
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%
Subsequent Event | 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]
Acres of rights conveyed | a				70
Partial interest in remaining acres conveyed (percentage)				32.00%
Subsequent Event | Dominion Gas Holdings, LLC | Marcellus Shale | Shale development rights | Amended Agreement to Extend Conveyance of Development Rights | Operations and Maintenance Expense
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deferred revenue recognized from conveyance of rights				$ 36,000,000
Deferred revenue recognized from conveyance of rights, after tax				22,000,000
Questar Corporation
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liabilities incurred		$ 3,900,000,000
Questar Corporation | Scenario, Forecast
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Price per share | $ / shares	$ 25
Acquisition price	$ 4,400,000,000
Debt acquired expected to remain outstanding	1,500,000,000
Termination fee to be paid by Dominion if acquisition is unapproved	154,000,000
Termination fee to be paid by Questar if acquisition is unapproved	$ 99,000,000
Questar Corporation | Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Liabilities incurred				$ 3,140,000,000
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%
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%
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														$ 197,000,000
Four Brothers
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Acquisition price									$ 64,000,000
Liabilities incurred									$ 62,000,000
Expected generation capacity of facilities (mw) | MW									320
Percentage of equity interests acquired									50.00%
Acquisition price in cash									$ 2,000,000
Number of solar development projects | Project									4
Expected cost of projects													$ 730,000,000	730,000,000
Acquired equity									$ 64,000,000
Non-controlling interest									25,000,000
Net property, plant and equipment acquired									$ 89,000,000
Four Brothers | Four Brothers | Obligation to Contribute Capital to Fund Construction of Projects
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount obligated to contribute to fund construction of projects													445,000,000	445,000,000
Contributions to fund projects													301,000,000	301,000,000
Four Brothers | Other Current Liabilities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payable at period end													20,000,000	20,000,000
Three Cedars
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Acquisition price								$ 43,000,000
Liabilities incurred								$ 37,000,000
Expected generation capacity of facilities (mw) | MW								210
Percentage of equity interests acquired								50.00%
Acquisition price in cash								$ 6,000,000
Number of solar development projects | Project								3
Expected cost of projects													425,000,000	425,000,000
Acquired equity								$ 43,000,000
Non-controlling interest								22,000,000
Net property, plant and equipment acquired								$ 65,000,000
Three Cedars | Four Brothers | Obligation to Contribute Capital to Fund Construction of Projects
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contributions to fund projects													144,000,000	144,000,000
Three Cedars | Affiliate | Obligation to Contribute Capital to Fund Construction of Projects
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Amount obligated to contribute to fund construction of projects													276,000,000	276,000,000
Three Cedars | Other Current Liabilities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payable at period end													$ 18,000,000	$ 18,000,000
DCG
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Acquisition price											$ 497,000,000
Percentage of equity interests acquired											100.00%
Net property, plant and equipment acquired											$ 277,000,000
Length of natural gas pipeline | mi											1,500
Goodwill											$ 250,000,000
Goodwill expected to be deductible for income tax purposes											225,000,000
Regulatory liabilities assumed											$ 38,000,000

[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.