Commitments and Contingencies (Narrative) (Detail) shares in Millions		1 Months Ended														3 Months Ended		12 Months Ended
	Oct. 31, 2014 MGD Facility	Jul. 31, 2023 USD ($)	Jun. 30, 2023 USD ($)	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	Nov. 30, 2019 gal	Jun. 30, 2018 USD ($)	Sep. 30, 2017 Petition	Apr. 30, 2017 Petition	Aug. 31, 2016 T	Mar. 31, 2024 USD ($) Indicator Facility Product	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Loss Contingencies [Line Items]
Number of DESC facilities subject to final regulations | Facility	5
Measurement of groundwater withdrawals | gal											3,000,000
Number of manufacturing gas plant decommissioned sites that contain residues of byproduct chemicals | Product																4
Estimated environmental remediation activities at manufacturing gas plant sites																$ 5,000,000
Environmental remediation costs recognized in regulatory assets																$ 34,000,000
Number of facilities inactive subject to final rule | Facility																3
Proportionate ownership share in project												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
Nuclear Insurance
Loss Contingencies [Line Items]
Maximum liability protection per nuclear incident amount																$ 16,300,000,000		$ 16,200,000,000
Maximum liability each nuclear plant is insured against																500,000,000		$ 450,000,000
Surety Bonds
Loss Contingencies [Line Items]
Guarantee obligation																$ 24,000,000
SCDOR
Loss Contingencies [Line Items]
Fair value of certain additional utility property transferred																			$ 3,000,000
Fair value of certain remaining utility property transferred			$ 11,000,000
Fair value of certain non-utility property transferred				$ 28,000,000
Fair value of certain utility property transferred																	$ 10,000,000
Gain from transferred utility property																	9,000,000
Gain from transferred utility property, after tax																	$ 7,000,000
Common Stock | Dominion Energy
Loss Contingencies [Line Items]
Litigation settlement through cash								$ 43,000,000
Shares issued on settlement | shares						0.9	0.6
Unfavorable Regulatory Action | CWA
Loss Contingencies [Line Items]
Electric generating stations with water withdrawals with heightened entrainment analysis under CWA | MGD	2
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]
Impairment of assets and other charges																$ 6,000,000
Maximum [Member] | SCDOR
Loss Contingencies [Line Items]
Cash payment		$ 1,000,000
Carbon Regulations [Member]
Loss Contingencies [Line Items]
Significant emission rate per year CO2 equivalent | T															75,000
EPA
Loss Contingencies [Line Items]
Number of petition agreed for reconsideration | Petition													2
EPA | Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Electric generating stations with water withdrawals under CWA | MGD	125
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
Environmental Protection Agency And State Regulatory Agencies
Loss Contingencies [Line Items]
Number of DESC hydroelectric facilities subject to regulations | Facility	5