Operating Revenue (Schedule of Operating Revenue) (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	$ 3,785	$ 3,758	$ 10,764	$ 10,290
Renewable Energy Investment Tax Credits
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	10	7	22	36
Alternative Revenue Programs
Public Utilities General Disclosures [Line Items]
Other revenues	24	34	85	111
Transition services agreements
Public Utilities General Disclosures [Line Items]
Other revenues	17	3	34	16
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	2,705	2,598	7,590	7,133
Virginia Electric and Power Company | Renewable Energy Investment Tax Credits
Public Utilities General Disclosures [Line Items]
Operating revenue from contracts with customers	$ 4	$ 2	$ 9	$ 24