Related-Party Transactions (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Related Party Transaction [Line Items]
Services provided to affiliates		$ 3,810	$ 3,963	$ 10,859	$ 10,135
Virginia Electric and Power Company
Related Party Transaction [Line Items]
Commodity purchases from affiliates		146	515	463	1,099
Services provided to affiliates	[1]	2,645	2,875	7,280	7,217
Virginia Electric and Power Company | Related Party
Related Party Transaction [Line Items]
Services provided by affiliates	[2]	149	125	441	378
Services provided to affiliates		$ 7	$ 4	$ 15	$ 13

[1] See Note 19 for amounts attributable to affiliates.

[2] Includes capitalized expenditures of $51 million and $44 million for the three months ended September 30, 2023 and 2022, respectively, and $151 million and $122 million for the nine months ended September 30, 2023 and 2022, respectively.