Fair Value Measurements (Narrative) (Detail) - USD ($)		3 Months Ended			6 Months Ended
		Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gains (losses) included in operating revenue in Level 3 fair value category		$ 2,000,000	$ 2,000,000		$ (6,000,000)	$ 2,000,000
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	[1]	81,000,000	168,000,000		195,000,000	449,000,000
Impairment of assets and other charges		67,000,000	37,000,000		97,000,000	135,000,000
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent		81,000,000	168,000,000		195,000,000	449,000,000
Level 2 | Nonregulated Solar Assets
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
Impairment of Assets and Other Charges | Nonregulated Solar Assets
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
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		$ 91,000,000
Asset impairment charges after tax		12,000,000		$ 68,000,000
Virginia Electric and Power Company
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gains (losses) included in operating revenue in Level 3 fair value category		$ 0	$ 0		$ 0	$ 0

[1] Includes income tax expense (benefit) of $(19) million and $38 million for the three months ended June 30, 2024 and 2023, respectively, and $32 million and $94 million for the six months ended June 30, 2024 and 2023, respectively.