Commitments and Contingencies (Narrative) (Detail) shares in Millions		1 Months Ended							3 Months Ended
	Oct. 31, 2014 MGD Facility	May 31, 2022 shares	Aug. 31, 2021 shares	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Feb. 28, 2019 USD ($)	Jun. 30, 2018 USD ($)	Aug. 31, 2016 T	Mar. 31, 2022 USD ($) Product	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)
Loss Contingencies [Line Items]
Electric generating stations with water withdrawals under CWA | MGD	125
Electric generating stations with water withdrawals with heightened entrainment analysis under CWA | MGD	2
Number of DESC facilities subject to final regulations | Facility	5
Number of DESC hydroelectric facilities subject to regulations | Facility	5
Number of manufacturing gas plant decommissioned sites that contain residues of byproduct chemicals | Product									4
Estimated environmental remediation activities at manufacturing gas plant sites									$ 26,000,000
Environmental remediation costs recognized in regulatory assets									38,000,000
Reserves for litigation and regulatory proceedings									194,000,000		$ 211,000,000
Insurance receivables									85,000,000		85,000,000
Impairment of assets and other charges									0	$ 60,000,000
Amount claimed by plaintiffs in legal matter						$ 100,000,000
Proportionate ownership share in project						100.00%	100.00%
Proposed assessment amount from SCDOR audit							$ 410,000,000
Litigation settlement expense awarded					$ 165,000,000
Common Stock | Dominion Energy
Loss Contingencies [Line Items]
Litigation settlement through cash				$ 43,000,000
Shares issued on settlement | shares			0.6
Common Stock | Forecast | Dominion Energy
Loss Contingencies [Line Items]
Shares issued on settlement | shares		0.9
Personal Injury or Wrongful Death Cases
Loss Contingencies [Line Items]
Insurance receivables									70,000,000		$ 85,000,000
Impairment of Assets and Other Charges | Dominion Energy South Carolina, Inc.
Loss Contingencies [Line Items]
Impairment of assets and other charges									0	60,000,000
Impairment of assets and other charges, after-tax									$ 0	$ 45,000,000
Carbon Regulations [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Significant emission rate per year CO2 equivalent | T								75,000