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Derivatives and Hedge Accounting Activities (Schedule of Derivatives not Designated as Hedging Instruments) (Detail) - Derivatives Not Designated as Hedging Instruments - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2018 | Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | $ (7) | $ (4)
Virginia Electric and Power Company |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [2] |  | (17)
Commodity | Virginia Electric and Power Company |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [2],[3] |  | (17)
Commodity | Operating Revenue |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | 6 | 4
Commodity | Purchased Gas |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] |  | 16
Commodity | Electric Fuel and Other Energy-Related Purchases |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | $ (13) | (23)
Commodity | Other operations and maintenance |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] |  | $ (1)
[1] | Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in Dominion Energy’s Consolidated Statements of Income.
[2] | Includes derivative activity amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in Virginia Power’s Consolidated Statements of Income.
[3] | Amounts recorded in Virginia Power's Consolidated Statements of Income are classified in electric fuel and other energy-related purchases.

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959 + 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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