Acquisitions and Dispositions (Disposition of Gas Transmission & Storage Operations) (Narrative) (Detail) - Q-Pipe Group - Southwest Gas $ in Millions	3 Months Ended
Mar. 31, 2022 USD ($)
Business Acquisition And Dispositions [Line Items]
Gain (loss) on held for sale	$ 27,000
Gain (loss) on held for sale, after tax	20,000
Transition Service Agreement
Business Acquisition And Dispositions [Line Items]
Operating revenue	$ 1
Disposal group, administrative services description	Dominion Energy will continue to provide specified administrative services to support the operations of the disposed businesses for up to 12 months after closing, subject to extension.

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Amount of revenue attributable to disposal group, including, but not limited to, discontinued operation.

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Amount before tax of gain (loss) recognized on the sale or disposal of a disposal group. Excludes discontinued operations.

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