Accumulated Other Comprehensive Income (Loss) (Schedule of Changes in AOCI Net of Tax and Reclassifications out of AOCI by Component) (Parenthetical) (Detail) - USD ($) $ in Millions	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Total Derivative-Hedging Activities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount of tax	$ 58	$ 61	$ 58	$ 64	$ 68	$ 73
Total Derivative-Hedging Activities \| Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount of tax	(8)	(7)	(10)	(8)	(7)	(5)
Investment Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount of tax	0	2	9	6	11	(1)
Investment Securities \| Virginia Electric and Power Company
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount of tax	1	1	1	1	3	1
Pension and Other Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amount of tax	$ (8)	$ (9)	$ (9)	$ (11)	$ (10)	$ (14)

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details