Equity (Schedule of Changes in AOCI Net of Tax and Reclassifications out of AOCI by Component) (Parenthetical) (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Total Derivative-Hedging Activities
Accumulated Other Comprehensive Income Loss [Line Items]
Amount of tax	$ 58	$ 73	$ 83
Total Derivative-Hedging Activities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Amount of tax	(10)	(5)	(5)
Investment Securities
Accumulated Other Comprehensive Income Loss [Line Items]
Amount of tax	5	(2)	13
Investment Securities | Virginia Electric and Power Company
Accumulated Other Comprehensive Income Loss [Line Items]
Amount of tax			2
Pension and Other Postretirement Benefit Costs
Accumulated Other Comprehensive Income Loss [Line Items]
Amount of tax	$ (9)	$ (14)	(19)
Equity Method Investees
Accumulated Other Comprehensive Income Loss [Line Items]
Amount of tax			$ 1