[Line Items] for Significant Accounting Policies [Table]

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- Definition

Utilities operating expense, increase (decrease) in depreciation and amortization.

+ References

No definition available.

+ Details

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- Definition

Utilities operating expense, increase (decrease) in depreciation and amortization, after tax.

+ References

No definition available.

+ Details

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- Definition

Percentage investment held by members or limited partners of limited liability company (LLC) or limited partnership (LP).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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No definition available.

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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No definition available.

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Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Sep. 30, 2015
Change in Estimated Useful Life \| Merchant generation assets
Significant Accounting Policies [Line Items]
Increase (decrease) in depreciation expense	$ (13)
Increase (decrease) in depreciation expense, after tax	$ (8)
Change in Estimated Useful Life \| Scenario, Forecast \| Merchant generation assets
Significant Accounting Policies [Line Items]
Increase (decrease) in depreciation expense		$ (26)
Increase (decrease) in depreciation expense, after tax		(16)
Four Brothers and Three Cedars
Significant Accounting Policies [Line Items]
Percentage ownership in total units	50.00%
Dominion Energy Midstream Partners, LP \| Common and Subordinated Units
Significant Accounting Policies [Line Items]
Ownership interest percentage of limited partner interests	50.90%
Dominion Energy Midstream Partners, LP \| Convertible Preferred Interests
Significant Accounting Policies [Line Items]
Ownership interest percentage of limited partner interests	37.50%
NRG Energy, Inc \| Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Merchant Solar Projects
Significant Accounting Policies [Line Items]
Percentage of equity interest sold to noncontrolling interest owners	33.00%		33.00%
Virginia Electric and Power Company \| Change in Depreciation Rates from New Depreciation Study
Significant Accounting Policies [Line Items]
Increase (decrease) in depreciation expense	$ 22
Increase (decrease) in depreciation expense, after tax	$ 13
Virginia Electric and Power Company \| Change in Depreciation Rates from New Depreciation Study \| Scenario, Forecast
Significant Accounting Policies [Line Items]
Increase (decrease) in depreciation expense		40
Increase (decrease) in depreciation expense, after tax		$ 25