Investments (Equity and Fixed Income Securities, Insurance Contracts and Cash Equivalents in Decommissioning Trust Funds) (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Net assets related to pending sales of securities	$ 42
Net assets related to pending purchases of securities		$ 35
Fair value of securities in an unrealized loss position	1,600	883
Virginia Electric and Power Company
Debt and Equity Securities, FV-NI [Line Items]
Net assets related to pending sales of securities	24	5
Fair value of securities in an unrealized loss position	$ 946	$ 425

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
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-Topic 320
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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