Commitments and Contingencies (Narrative) (Detail) shares in Millions		1 Months Ended											3 Months Ended			9 Months Ended
	Oct. 31, 2014 MGD Facility	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	May 31, 2022 shares	Aug. 31, 2021 shares	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Oct. 31, 2020	Jun. 30, 2018 USD ($)	Aug. 31, 2017 USD ($)	Apr. 30, 2017 Petition	Aug. 31, 2016 T	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Sep. 30, 2022 USD ($) Facility Indicator Product	Sep. 30, 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																$ 21,000,000
Environmental remediation costs recognized in regulatory assets		$ 38,000,000											$ 38,000,000			$ 38,000,000
Number of facilities inactive subject to final rule | Facility																3
Reserves for litigation and regulatory proceedings		96,000,000											96,000,000			$ 96,000,000		$ 211,000,000
Insurance receivables		68,000,000											68,000,000			68,000,000		85,000,000
Impairment of assets and other charges																4,000,000	$ 320,000,000
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
Real estate transfer to satisfy obligation under settlement			$ 51,000,000
Maximum liability protection per nuclear incident amount													13,700,000,000	$ 13,500,000,000
Summer
Loss Contingencies [Line Items]
Nuclear property insurance coverage amount														1,060,000,000.00	$ 2,750,000,000
NEIL maximum retrospective premium assessment														11,000,000
SCDOR [Member]
Loss Contingencies [Line Items]
Value of certain utility and non-utility properties to be conveyed		3,000,000											3,000,000			3,000,000
Expected gain on transfer of remaining utility and non-utility properties		20,000,000
Non utility property fair value		28,000,000
Common Stock | Dominion Energy
Loss Contingencies [Line Items]
Litigation settlement through cash						$ 43,000,000
Shares issued on settlement | shares				0.9	0.6
Impairment of Assets and Other Charges | Dominion Energy South Carolina, Inc.
Loss Contingencies [Line Items]
Impairment of assets and other charges																	70,000,000
Impairment of assets and other charges, after-tax																	$ 53,000,000
Other Income | SCDOR [Member]
Loss Contingencies [Line Items]
Gain from transferred non utility property													19,000,000			19,000,000
Gain from transferred non utility property, after tax													14,000,000			$ 14,000,000
Unfavorable Regulatory Action | CWA
Loss Contingencies [Line Items]
Number of mandatory facility specific factors. | Indicator																5
Number of optional facility specific factors | Indicator																6
Personal Injury or Wrongful Death Cases
Loss Contingencies [Line Items]
Reserves for litigation and regulatory proceedings		68,000,000											68,000,000			$ 68,000,000		85,000,000
Insurance receivables		$ 68,000,000											$ 68,000,000			$ 68,000,000		$ 85,000,000
Carbon Regulations [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Significant emission rate per year CO2 equivalent | T												75,000
EPA | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Number of separate petitions for reconsideration granted | Petition											2
EPA | Minimum [Member] | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies Individual circumstances period								2021
EPA | Maximum [Member] | Unfavorable Regulatory Action | CWA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies Individual circumstances period								2028
European Mutual Association | Summer
Loss Contingencies [Line Items]
Nuclear property insurance coverage amount														$ 1,000,000	$ 415,000,000