Commitments and Contingencies (Narrative) (Detail) shares in Millions, $ in Millions		1 Months Ended											3 Months Ended			6 Months Ended
	Oct. 31, 2014 MGD Facility	Jul. 31, 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	Jun. 30, 2022 USD ($)	Mar. 31, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) Facility Indicator Product	Jun. 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																$ 26
Environmental remediation costs recognized in regulatory assets			$ 38										$ 38			$ 38
Number of facilities inactive subject to final rule | Facility																3
Reserves for litigation and regulatory proceedings			124										124			$ 124		$ 211
Insurance receivables			68										68			68		85
Impairment of assets and other charges																4	$ 319
Amount claimed by plaintiffs in legal matter										$ 100
Proportionate ownership share in project									100.00%	100.00%
Proposed assessment amount from SCDOR audit									$ 410
Litigation settlement expense awarded							$ 165
Real estate transfer to satisfy obligation under settlement			51
Expected gain on utility and non-utility properties to be conveyed													(15)		$ 0	$ (18)	0
Summer
Loss Contingencies [Line Items]
Nuclear property insurance coverage amount													1,060	$ 2,750
NEIL maximum retrospective premium assessment													11
SCDOR [Member] | Subsequent Event
Loss Contingencies [Line Items]
Value of certain utility and non-utility properties to be conveyed		$ 31
Expected gain on utility and non-utility properties to be conveyed		20
Expected gain on transfer of remaining utility and non-utility properties		$ 20
Common Stock | Dominion Energy
Loss Contingencies [Line Items]
Litigation settlement through cash						$ 43
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															10		70
Impairment of assets and other charges, after-tax															$ 8		$ 53
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										68			$ 68		85
Insurance receivables			$ 68										68			$ 68		$ 85
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	$ 415