Commitments and Contingencies (Narrative) (Detail)			1 Months Ended												3 Months Ended	12 Months Ended
	Apr. 30, 2015 Facility	Oct. 31, 2014 MGD Facility	Dec. 31, 2021 USD ($)	Aug. 31, 2021 shares	Jul. 31, 2021 USD ($) shares	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Aug. 31, 2020 USD ($)	Jul. 31, 2019 USD ($)	Feb. 28, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Aug. 31, 2016 T	Mar. 31, 2019 USD ($)	Dec. 31, 2021 USD ($) Product	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2020 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 MGP decommissioned sites that contain residues of byproduct chemicals | Product																4
Estimated environmental remediation activities at MGP sites																$ 19,000,000
Estimated increase in remediation costs for Congaree River site																11,000,000
Environmental remediation costs recognized in regulatory assets			$ 31,000,000													31,000,000
Number of CCR landfills facilities subject to final rule | Facility	3
Impairment of assets and other charges															$ 105,000,000	311,000,000	$ (14,000,000)	$ 576,000,000
Impairment of assets and other charges, after-tax															79,000,000
Customer refundable fees, alternative plan			3,181,000,000				$ 3,288,000,000									3,181,000,000	3,288,000,000
Regulatory liability for refunds to natural gas customers															2,000,000
Regulatory liability for refunds to natural gas customers, after tax															2,000,000
Reserves for litigation and regulatory proceedings			211,000,000				208,000,000									211,000,000	208,000,000
Insurance receivables			85,000,000				8,000,000									85,000,000	8,000,000
Settlement payable by all																			$ 520,000,000
Settlement payable by company					$ 99,000,000						$ 100,000,000								320,000,000
Proportionate ownership share in project											100.00%		100.00%
Litigation settlement expense					$ 99,000,000						$ 100,000,000								$ 320,000,000
Proposed assessment amount from SCDOR audit													$ 410,000,000
Agreement in principle to resolve the SCDOR matter							165,000,000
Contesting Amount For Filed Liens																285,000,000
Energy payments under power purchase contracts			73,000,000				$ 64,000,000									73,000,000	64,000,000	37,000,000
Summer
Loss Contingencies [Line Items]
Proceeds from legal settlements of share of claims incurred in previous year																1,000,000	4,000,000
Nuclear Insurance
Loss Contingencies [Line Items]
Maximum liability each nuclear plant is insured against			450,000,000													$ 450,000,000
Inflation adjustment period for nuclear insurance																5 years
NEIL maximum insurance coverage to nuclear facility for property damage and outage costs			2,750,000,000													$ 2,750,000,000
NEIL maximum insurance coverage to nuclear facility for property damage and outage costs from non-nuclear event																2,330,000,000
NEIL aggregate maximum loss for any single loss occurrence			$ 2,750,000,000													2,750,000,000
NEIL maximum retrospective premium assessment																24,000,000
EMANI maximum insurance coverage for Summer station unit 1 for property damage and outage costs from non-nuclear event																415,000,000
EMANI maximum retrospective premium assessment																$ 2,000,000
N N D Project
Loss Contingencies [Line Items]
Jointly owned utility plant, proportionate ownership share			55.00%													55.00%
Common Stock | Dominion Energy
Loss Contingencies [Line Items]
Common stock issued to satisfy the settlement								$ 322,000,000
Litigation settlement through stock issuance | shares				600,000	1,400,000
Litigation settlement through cash						$ 43,000,000
SCANA
Loss Contingencies [Line Items]
Payment of civil monetary penalty																	25,000,000
SCANA and DESC
Loss Contingencies [Line Items]
Payment of disgorgement and prejudgment interest																	112,500,000
Impairment of Assets and Other Charges | Dominion Energy South Carolina, Inc.
Loss Contingencies [Line Items]
Impairment of assets and other charges																$ 70,000,000	97,000,000	590,000,000
Impairment of assets and other charges, after-tax																53,000,000	73,000,000	$ 444,000,000
SCANA Combination
Loss Contingencies [Line Items]
Regulatory asset impairment charges committed to forgo recovery															258,000,000
Tax charge related to regulatory assets committed to forgo recovery															194,000,000
DESC Ratepayer Case
Loss Contingencies [Line Items]
Customer refundable fees, alternative plan															1,000,000,000.0
Customer refund fees alternative plan after tax															$ 756,000,000
Customer refunded estimated period															11 years
Previous existing regulatory liability															$ 1,000,000,000.0
Previous existing regulatory liability, years															20 years
Escrow amount												$ 2,000,000,000.0
Credit in future electric rate relief for ratepayer case												2,000,000,000.0
Cash payment related to Ratepayer Case										$ 117,000,000		115,000,000
Property with net value transferred			$ 8,000,000						$ 22,000,000
Property with net value transferred, cash contribution								38,500,000
Conveyance of property with net recorded value								$ 3,000,000
DESC Ratepayer Case | Common Stock | Dominion Energy
Loss Contingencies [Line Items]
Common stock issued to satisfy the settlement																	$ 322,000,000
Maximum [Member] | Nuclear Insurance
Loss Contingencies [Line Items]
Maximum liability protection per nuclear incident amount																13,500,000,000
Amount that could be assessed for each licensed reactor			138,000,000													138,000,000
Amount that could be assessed for each licensed reactor per year																21,000,000
Maximum [Member] | DESC Summer | Nuclear Insurance
Loss Contingencies [Line Items]
Amount that could be assessed for each licensed reactor			$ 92,000,000													92,000,000
Amount that could be assessed for each licensed reactor per year																$ 14,000,000
Maximum [Member] | DESC Ratepayer Case
Loss Contingencies [Line Items]
Estimated aggregate fair value of certain real estate												85,000,000
Minimum [Member] | DESC Ratepayer Case
Loss Contingencies [Line Items]
Estimated aggregate fair value of certain real estate												$ 60,000,000
Carbon Regulations [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Significant emission rate per year CO2 equivalent | T														75,000