Concentration Risk and Guarantor Obligations [Line Items]

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- Definition

Concentration risk, credit risk, financial instrument, maximum exposure for single counterparty.

+ References

No definition available.

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- Definition

Concentration risk credit risk number of counterparties.

+ References

No definition available.

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- Definition

Letter of credit as collateral posted for derivatives in liability position fair value.

+ References

No definition available.

+ Details

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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://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 185
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-185

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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://www.xbrl.org/2003/role/exampleRef
-Topic 815
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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://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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- Definition

The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 185
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-185

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Credit Risk (Narrative) (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
Credit Risk (Narrative) (Detail)	Sep. 30, 2026 USD ($) Counterparty	Sep. 30, 2025	Sep. 30, 2026 USD ($) Counterparty	Sep. 30, 2025	Dec. 31, 2025 USD ($)
Concentration Risk and Guarantor Obligations [Line Items]
Credit exposure			$ 786,000,000
Number of counterparties \| Counterparty	0		0
Amount of exposure for single counterparty			$ 443,000,000
Additional collateral to be posted if the credit related contingent features were triggered	$ 33,000,000		33,000,000		$ 29,000,000
Collateral derivatives with credit-related contingent provision in a liability position	0		0		0
Aggregate fair value of all derivative instruments with credit contingent provisions that are in a liability position	33,000,000		33,000,000		29,000,000
Letter of credit as collateral posted for derivatives in liability position	$ 0		0		0
Virginia Electric and Power Company
Concentration Risk and Guarantor Obligations [Line Items]
Credit exposure			$ 39,000,000
Number of counterparties \| Counterparty	0		0
Amount of exposure for single counterparty			$ 18,000,000
Additional collateral to be posted if the credit related contingent features were triggered	$ 0		0		0
Collateral derivatives with credit-related contingent provision in a liability position	0		0		0
Aggregate fair value of all derivative instruments with credit contingent provisions that are in a liability position	0		0		0
Letter of credit as collateral posted for derivatives in liability position	$ 0		$ 0		$ 0
Credit Concentration Risk \| Investment Grade Counterparty \| Virginia Electric and Power Company
Concentration Risk and Guarantor Obligations [Line Items]
Concentration risk, percentage (percentage)			90.00%
Credit Concentration Risk \| Investment Grade \| Investment Grade Counterparty
Concentration Risk and Guarantor Obligations [Line Items]
Concentration risk, percentage (percentage)			99.00%
Customer Concentration Risk \| Total Operating Revenue \| Virginia Electric and Power Company
Concentration Risk and Guarantor Obligations [Line Items]
Concentration risk, percentage (percentage)	10.00%	9.00%	12.00%	9.00%
Customer Concentration Risk \| Customer Receivables \| Virginia Electric and Power Company
Concentration Risk and Guarantor Obligations [Line Items]
Concentration risk, percentage (percentage)			6.00%		10.00%