Investments (Portion of Unrealized Gains and Losses Relates to Equity Securities) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Debt Securities, Available-for-Sale [Line Items]
Net gains (losses) recognized during the period		$ 178	$ 294	$ 637	$ 520
Less: Net (gains) losses recognized during the period on securities sold during the period		6	1	(4)	3
Unrealized gains (losses) recognized during the period on securities still held at period end	[1]	184	295	633	523
Virginia Electric and Power Company
Debt Securities, Available-for-Sale [Line Items]
Net gains (losses) recognized during the period		86	153	328	269
Less: Net (gains) losses recognized during the period on securities sold during the period		4	2	(5)	3
Unrealized gains (losses) recognized during the period on securities still held at period end	[1]	$ 90	$ 155	$ 323	$ 272

[1] Included in other income (expense) and the nuclear decommissioning trust regulatory liability.