Regulatory Assets and Liabilities (Narrative) (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Public Utilities General Disclosures [Line Items]
Regulatory assets not expect to earn return	$ 4,800
Period for which expenditures are expected to be recovered	2 years
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Regulatory assets not expect to earn return	$ 3,400
Period for which expenditures are expected to be recovered	2 years
Dominion Energy Gas Holdings, LLC
Public Utilities General Disclosures [Line Items]
Regulatory assets not expect to earn return	$ 48
Period for which expenditures are expected to be recovered	2 years