Commitments and Contingencies (Environmental Matters) (Narrative) (Detail) $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended
	Oct. 31, 2020	Apr. 30, 2017 Petition	Aug. 31, 2016 T	Jun. 30, 2022 Site	Dec. 31, 2023 USD ($) Indicator Site Facility gal	Dec. 31, 2022 USD ($)
Unfavorable Regulatory Action | EPA
Loss Contingencies [Line Items]
Electric generating stations with water withdrawals per day | gal					2,000,000
Electric generating station facilities heightened entrainment analysis per day | gal					125,000,000
Carbon Regulations
Loss Contingencies [Line Items]
Public Utilities Significant Emission Rate Per Year CO2 Equivalent | T			75,000
CWA | Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Number of mandatory facility-specific factors | Indicator					5
Number of optional facility-specific factors | Indicator					6
Number of facilities that are subject to final regulations | Facility					15
CWA | Unfavorable Regulatory Action | EPA | 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
Waste Management and Remediation | Unfavorable Regulatory Action | EPA
Loss Contingencies [Line Items]
Number of sites remediation work substantially completed					14
Number of sites with remediation plans				1
Number of additional sites which are not under investigation					12
Waste Management and Remediation | Unfavorable Regulatory Action | EPA | Former Gas Plant Site With Post Closure Groundwater Monitoring Program
Loss Contingencies [Line Items]
Environmental remediation reserves | $					$ 32	$ 47
Minimum | CWA | Unfavorable Regulatory Action | EPA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies individual circumstances period	2021
Maximum | CWA | Unfavorable Regulatory Action | EPA | Final Rule to Revise Effluent Limitations Guidelines for Steam Electric Power Generating Category
Loss Contingencies [Line Items]
Loss contingencies individual circumstances period	2028
Virginia Electric and Power Company | Environmental Protection Agency And State Regulatory Agencies
Loss Contingencies [Line Items]
Number of facilities to assess the applicability of section 316(b) | Facility					3
Virginia Electric and Power Company | CWA | Unfavorable Regulatory Action
Loss Contingencies [Line Items]
Number of facilities that are subject to final regulations | Facility					9
Virginia Electric and Power Company | Waste Management and Remediation | Unfavorable Regulatory Action | EPA
Loss Contingencies [Line Items]
Number of sites with remediation plans					1
Number of additional sites which are not under investigation					2
Virginia Electric and Power Company | Waste Management and Remediation | Unfavorable Regulatory Action | EPA | Former Gas Plant Site With Post Closure Groundwater Monitoring Program
Loss Contingencies [Line Items]
Environmental remediation reserves | $					$ 25	$ 25
Hydroelectric Facilities | Environmental Protection Agency And State Regulatory Agencies
Loss Contingencies [Line Items]
Number of facilities to assess the applicability of section 316(b) | Facility					8