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Significant Accounting Policies (Schedule of Supplemental Cash Flow Information) (Parenthetical) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Schedule Of Supplemental Cash Flow Information [Line Items] |  |
Financing leases | $ 46 | $ 113
Operating leases | 127 | 44
Virginia Electric and Power Company |  |
Schedule Of Supplemental Cash Flow Information [Line Items] |  |
Financing leases | $ 32 | 20
Operating leases |  | $ 35

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- Definition Financing leases. + References No definition available. + Details
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Namespace Prefix: | d_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Operating Leases + References No definition available. + Details
Name: | d_OperatingLeases
Namespace Prefix: | d_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Schedule of supplemental cash flow information. + References No definition available. + Details
Name: | d_ScheduleOfSupplementalCashFlowInformationLineItems
Namespace Prefix: | d_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | dei_LegalEntityAxis=d_VirginiaElectricAndPowerCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |