Rate and Other Regulatory Matters (Narrative) (Detail) - USD ($) $ in Millions		1 Months Ended								3 Months Ended			6 Months Ended	12 Months Ended
	Sep. 01, 2021	Feb. 28, 2022	Feb. 25, 2022	Oct. 31, 2021	Jul. 31, 2021	Jun. 30, 2021	May 31, 2021	Apr. 30, 2021	Aug. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Feb. 25, 2021
Rate And Other Regulatory Matters [Line Items]
Percentage of current authorized earned ROE				9.90%
Other asset impairment charges													$ 249
Other asset impairment charges after tax													187
Purchase of first mortgage bond													$ 237
Recovery under settlement agreement														$ 18
Recovery under settlement agreement after tax														$ 14
South Carolina Commission Order for Increase/Decrease of Total Fuel Cost Component of Retail Electric Rates to produce a projected under-recovery			$ 143														$ 36
South Carolina Commission Order, Annual DSM Program Rate Rider Recovery Amount								$ 60
Annual increase (decrease) in pension cost rider		$ (12)
South Carolina Commission order, revenue requirement under RSA				$ 424		$ 426
South Carolina Commission order, increase in natural gas rates under RSA				$ 7		$ 9
Regulatory asset recovery assessment end period														2047
Impairment of assets and other charges												$ 105		$ 311	$ (14)	$ 576
Monetization Of Guaranty Settlement [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers over period														20 years
End period for recovery														2039
Income Taxes Refundable Through Future Rates [Member]
Rate And Other Regulatory Matters [Line Items]
Remaining lives of related property period														85 years
Reserve For Refunds To Electric Utility Customers [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers over period														11 years
Deferred Losses or Gains On Interest Rate Derivatives [Member]
Rate And Other Regulatory Matters [Line Items]
Changes in fair value and payments of interest rate derivatives designated as cash flow hedge, amortized to interest expense, year														2043
Changes in fair value and payments of interest rate derivatives not designed, amortized to interest, year														2065
Dominion Energy South Carolina [Member]
Rate And Other Regulatory Matters [Line Items]
Impairment of assets and other charges														$ 237
Impairment of assets and other charges, after-tax														$ 178
NND Project Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers over period														20 years
End period for recovery														2039
Deferred Employee Benefit Plan Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Regulatory asset recovery assessment end period														2044
Average service period expected to recover other deferred benefit costs														11 years
Other Unrecovered Plant [Member]
Rate And Other Regulatory Matters [Line Items]
Remaining useful lives of coal-fired generating units, year														2025
New expected remaining useful lives of coal-fired generating units, year														2029
Recovery period for existing meters and equipment retired from service														2028
Demand Side Management Programs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset														3 years
Asset Retirement Obligation Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Recovery period of regulatory asset														105 years
Environmental Remediation Costs [Member]
Rate And Other Regulatory Matters [Line Items]
MPG environmental remediation														22 years
Maximum [Member]
Rate And Other Regulatory Matters [Line Items]
Annual increase (decrease) in pension cost rider								(1)
Rider D S M
Rate And Other Regulatory Matters [Line Items]
South Carolina Commission Order, Annual DSM Program Rate Rider Recovery Amount	$ 43							$ 48
South Carolina Electric Base Rate Case
Rate And Other Regulatory Matters [Line Items]
Amount of Increase in proposed non fuel base rate									$ 178
Increase in proposed non fuel base rate									7.75%
Percentage of ROE based on fully adjusted test period									5.90%
Percentage of current authorized earned ROE									10.25%
South Carolina Office Of Regulatory Staff And Other Parties [Member]
Rate And Other Regulatory Matters [Line Items]
Amount of Increase in proposed non fuel base rate					$ 62
Percentage of current authorized earned ROE					9.50%
Non fuel base rate increase after amortization					$ 36
Retail electric customer balance					15
Due days for forgive retail electric customer balance							60 days
Welfare charges for customers					$ 15
Toshiba Corporation [Member]
Rate And Other Regulatory Matters [Line Items]
Bankruptcy, amount of claims filed			$ 66
Savannah River Site
Rate And Other Regulatory Matters [Line Items]
Interest charges (benefit)										$ (10)	$ 6
Interest charges (benefit), after tax										$ (7)	$ 4