Goodwill and Intangible Assets (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Goodwill [Line Items]
Acquisition of intangible assets	$ 675
Weighted-average amortization period (years)	7 years
Software, Licenses and Other
Goodwill [Line Items]
Amortization expense for intangible assets	$ 87	$ 160	$ 103
Virginia Electric and Power Company
Goodwill [Line Items]
Acquisition of intangible assets	$ 605
Weighted-average amortization period (years)	6 years
Virginia Electric and Power Company | Software, Licenses and Other
Goodwill [Line Items]
Amortization expense for intangible assets	$ 51	$ 123	$ 67