Related-Party Transactions (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023		Dec. 31, 2022		Dec. 31, 2021
Related Party Transaction [Line Items]
Services provided to affiliates		$ 3,534	$ 3,810	$ 3,166	$ 3,883	$ 3,807	$ 3,961	$ 3,058	$ 3,112	$ 14,393		$ 13,938		$ 11,419
Virginia Electric and Power Company
Related Party Transaction [Line Items]
Commodity purchases from affiliates										582		1,423		742
Services provided to affiliates		$ 2,292	$ 2,645	$ 2,252	$ 2,384	$ 2,436	$ 2,875	$ 2,176	$ 2,167	9,573	[1]	9,654	[1]	7,470	[1]
Virginia Electric and Power Company | Related Party
Related Party Transaction [Line Items]
Services provided by affiliates	[2]									605		519		494
Services provided to affiliates										$ 20		$ 18		$ 18

[1] See Note 25 for amounts attributable to affiliates.

[2] Includes capitalized expenditures of $210 million, $177 million and $161 million for the years ended December 31, 2023, 2022 and 2021, respectively.