Operating Revenue (Schedule of Operating Revenue) (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	$ 3,758	$ 4,236	$ 10,290	$ 10,967
Renewable Energy Investment Tax Credits
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	7	21	36	32
Alternative Revenue Programs
Public Utilities General Disclosures [Line Items]
Other revenues	34	20	111	47
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	2,598	2,959	7,133	7,394
Virginia Electric and Power Company | Renewable Energy Investment Tax Credits
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	2	13	24	13
Virginia Electric and Power Company | Alternative Revenue Programs
Public Utilities General Disclosures [Line Items]
Other revenues	$ 34	$ 20	$ 111	$ 47