A description of the principal activities of an investee accounted for under the equity method.

No definition available.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

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- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66022249&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Investments (Investments Under Equity Method of Accounting) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 1,544	$ 1,561	$ 1,320
Iroquois
Schedule of Equity Method Investments [Line Items]
Ownership%	50.00%
Investment Balance	$ 311	316
Description	Gas transmission system
Blue Racer Midstream Llc [Member]
Schedule of Equity Method Investments [Line Items]
Ownership%	50.00%
Investment Balance	$ 691	677
Description	Midstream gas and related services
Atlantic Coast Pipeline
Schedule of Equity Method Investments [Line Items]
Ownership%	48.00%
Investment Balance	$ 382	256
Description	Gas transmission system
Fowler I Holdings LLC
Schedule of Equity Method Investments [Line Items]
Ownership%	50.00%
Investment Balance	$ 81	116
Description	Wind-powered merchant generation facility
Nedpower Mount Storm Llc [Member]
Schedule of Equity Method Investments [Line Items]
Ownership%	50.00%
Investment Balance		112
Description	Wind-powered merchant generation facility
Other Investment [Member]
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 79	84
Dominion Energy Gas Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 95	98	$ 102
Dominion Energy Gas Holdings, LLC \| Iroquois
Schedule of Equity Method Investments [Line Items]
Ownership%	24.07%
Investment Balance	$ 95	$ 98
Description	Gas transmission system