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Credit Risk (Narrative) (Detail) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 USD ($) counterparty | Dec. 31, 2019 USD ($)
Concentration Risk And Guarantor Obligations [Line Items] |  |
Gross credit exposure | $ 107,000,000 |
Additional collateral to be posted if the credit related contingent features were triggered | 14,000,000 | $ 10,000,000
Collateral derivatives with credit-related contingent provision in a liability position | 1,000,000 | 0
Aggregate fair value of all derivative instruments with credit contingent provisions that are in a liability position | 15,000,000 | 10,000,000
Virginia Electric and Power Company |  |
Concentration Risk And Guarantor Obligations [Line Items] |  |
Gross credit exposure | 15,000,000 |
Additional collateral to be posted if the credit related contingent features were triggered | 2,000,000 | $ 8,000,000
Credit Concentration Risk |  |
Concentration Risk And Guarantor Obligations [Line Items] |  |
Amount of exposure for single counterparty | $ 41,000,000 |
Number of counterparties | counterparty | 0 |
Credit Concentration Risk | Virginia Electric and Power Company |  |
Concentration Risk And Guarantor Obligations [Line Items] |  |
Amount of exposure for single counterparty | $ 6,000,000 |
Number of counterparties | counterparty | 0 |
Credit Concentration Risk | Investment Grade Counterparty | Virginia Electric and Power Company |  |
Concentration Risk And Guarantor Obligations [Line Items] |  |
Concentration risk, percentage (percentage) | 97.00% |
Credit Concentration Risk | Investment Grade | Investment Grade Counterparty |  |
Concentration Risk And Guarantor Obligations [Line Items] |  |
Concentration risk, percentage (percentage) | 96.00% |

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- Definition The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4H -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624258-113959 + Details
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- Definition The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4H -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624258-113959 + Details
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- Definition Maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13537-108611 + Details
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