Derivatives and Hedge Accounting Activities (Schedule of Offsetting Assets) (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Offsetting Assets [Line Items]
Derivative assets, not subject to a master netting or similar arrangement	$ 161	$ 143
Virginia Electric and Power Company
Offsetting Assets [Line Items]
Derivative assets, not subject to a master netting or similar arrangement	$ 11	$ 1

Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, not subject to a master netting arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-SubTopic 20
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483466/210-20-50-3

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-22

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