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Derivatives and Hedge Accounting Activities (Schedule of Derivatives not Designated as Hedging Instruments) (Detail) - Fair Value - Derivatives not under Hedge Accounting - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | $ 42 | $ (26) | $ (26)
Virginia Electric and Power Company |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [2] | (104) | (45) | 2
Commodity | Virginia Electric and Power Company |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [2],[3] | (104) | (45) | 2
Commodity | Operating Revenue |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | 73 | 41 | (11)
Commodity | Purchased Gas |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | (20) | (22) | 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] | (104) | (46) | (9)
Commodity | Discontinued operations |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | (11) | (2) | (10)
Interest rate | Discontinued operations |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | 5 | 0 | 0
Interest rate | Interest and Related Charges |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | 87 | 3 | 0
Foreign currency | Discontinued operations |  |  |  |
Derivative Instruments Gain Loss [Line Items] |  |  |  |
Amount of Gain (Loss) Recognized in Income on Derivatives | [1] | $ 12 | $ 0 | $ 0
[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/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=121590274&loc=SL5618551-113959 + Details
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