Investments (Portion of Unrealized Gains and Losses Relates to Equity Securities) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2025	Mar. 31, 2024
Debt Securities, Available-for-Sale [Line Items]
Net gains (losses) recognized during the period		$ (239)	$ 459
Less: Net (gains) losses recognized during the period on securities sold during the period		6	(10)
Unrealized gains (losses) recognized during the period on securities still held at period end	[1]	(233)	449
Virginia Electric and Power Company
Debt Securities, Available-for-Sale [Line Items]
Net gains (losses) recognized during the period		(121)	242
Less: Net (gains) losses recognized during the period on securities sold during the period		4	(9)
Unrealized gains (losses) recognized during the period on securities still held at period end	[1]	$ (117)	$ 233

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