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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 | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | $ (26) | $ (45) | $ (63)
Virginia Electric and Power Company |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [2] | 2 | (57) | (70)
Dominion Energy Gas Holdings, LLC |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives |  | (11) |  | 1
Commodity | Operating Revenue |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | (28) | 18 | 2
Commodity | Operating Revenue | Virginia Electric and Power Company |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [2],[3] | 2 | (57) | (70)
Commodity | Operating Revenue | Dominion Energy Gas Holdings, LLC |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives |  | (11) |  | 1
Commodity | Purchased Gas |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | 11 | (3) | 4
Commodity | Electric fuel and other energy-related purchases |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | $ (9) | (59) | (70)
Commodity | Other operations and maintenance |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] |  | $ (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] | Represents net derivative activity deferred into and amortized out of regulatory assets/liabilities. Amounts deferred into regulatory assets/liabilities have no associated effect in Virginia Power's Consolidated Statements of Income.

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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/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959 + Details
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