Related-Party Transactions (Detail) - Virginia Electric and Power Company - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Related Party Transaction [Line Items]
Commodity purchases from affiliates		$ 515	$ 219	$ 1,099	$ 526
Services provided by affiliates	[1]	125	116	378	363
Affiliated Entity
Related Party Transaction [Line Items]
Services provided to affiliates		$ 4	$ 6	$ 13	$ 15

[1] Includes capitalized expenditures of $44 million and $39 million for the three months ended September 30, 2022 and 2021, respectively, and $122 million and $121 million for the nine months ended September 30, 2022 and 2021, respectively.