Fair Value Measurements (Narrative) (Detail) - USD ($)	3 Months Ended									12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Dec. 31, 2024		Dec. 31, 2023		Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets and other charges										$ 600,000,000		$ 307,000,000		$ 1,401,000,000
Net Income (Loss) From Discontinued Operations	$ (3,000,000)	$ (15,000,000)	$ 97,000,000	$ 118,000,000	$ (33,000,000)	$ (541,000,000)	$ 168,000,000	$ 281,000,000		197,000,000	[1]	(125,000,000)	[1]	922,000,000	[1]
Net Income (Loss) From Discontinued Operations, after tax										197,000,000		(125,000,000)		922,000,000	[2]
Unrealized gains or losses included in earnings in Level 3 fair value category										(5,000,000)		7,000,000		0
Level 3 | Corporate Office Building
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived assets, estimated fair value	$ 23,000,000				35,000,000					23,000,000		35,000,000
Impairment of Assets and Other Charges | Corporate Office Building
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets and other charges										17,000,000		93,000,000
Asset impairment charges after tax										12,000,000		69,000,000
Virginia Electric and Power Company
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gains or losses included in earnings in Level 3 fair value category										0		0		$ 0
Virginia Electric and Power Company | Impairment of Assets and Other Charges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets and other charges									$ 191,000,000	25,000,000
Asset impairment charges after tax									$ 142,000,000	$ 18,000,000
Nonregulated Solar Assets | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived assets, estimated fair value					$ 22,000,000							22,000,000
Nonregulated Solar Assets | Impairment of Assets and Other Charges
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of assets and other charges												15,000,000
Asset impairment charges after tax												$ 11,000,000

[1] Includes income tax expense of $31 million, $1.3 billion and $207 million for the years ended December 31, 2024, 2023 and 2022, respectively.

[2] As discussed in Note 19, effective in June 2022 through its redemption in September 2022, the Series A Preferred Stock was considered to be mandatorily redeemable and was classified in current liabilities.