Investments (Portion of Unrealized Gains and Losses Relates to Equity Securities) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Net gains (losses) recognized during the period		$ 459	$ 226
Less: Net (gains) losses recognized during the period on securities sold during the period		(10)	2
Unrealized gains (losses) recognized during the period on securities still held at period end	[1]	449	228
Virginia Electric and Power Company
Debt Securities, Available-for-Sale [Line Items]
Net gains (losses) recognized during the period		242	116
Less: Net (gains) losses recognized during the period on securities sold during the period		(9)	1
Unrealized gains (losses) recognized during the period on securities still held at period end	[1]	$ 233	$ 117

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