Rate and Other Regulatory Matters (Narrative) (Detail) - USD ($) $ in Millions		1 Months Ended					3 Months Ended	6 Months Ended
	Sep. 01, 2021	Jul. 31, 2021	Jun. 30, 2021	May 31, 2021	Apr. 30, 2021	Aug. 31, 2020	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020
Rate And Other Regulatory Matters [Line Items]
Other asset impairment charges							$ 249	$ 249
Other asset impairment charges after tax							187	187
Purchase of first mortgage bond							237	237
Recovery under settlement agreement							18	18
Recovery under settlement agreement after tax							14	$ 14
South Carolina Commission order, revenue requirement under RSA			$ 426
South Carolina Commission order, increase in natural gas rates under RSA			$ 9
Regulatory asset recovery assessment end period								2047
Impairment of assets and other charges								$ 319	$ 2
Reserve For Refunds To Electric Utility Customers [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery period								11 years
Monetization Of Guaranty Settlement [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery 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
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, Inc.
Rate And Other Regulatory Matters [Line Items]
Impairment of assets and other charges							237
Impairment of assets and other charges, after-tax							$ 178
Storm restoration recovery period								10 years
Deferred depreciation and property taxes recovery period								40 years
NND Project Costs [Member]
Rate And Other Regulatory Matters [Line Items]
Electric service customers recovery 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]
Amortization of carrying value of coal-fired generating unit								2025
New expected amortization of carrying value of coal-fired generating unit								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]
Recovery period of regulatory asset								15 years
Maximum [Member]
Rate And Other Regulatory Matters [Line Items]
Annual increase (decrease) in pension cost rider					$ (1)
Fuel Component [Member]
Rate And Other Regulatory Matters [Line Items]
Annual increase (decrease) in total fuel cost component of retail electric rates					36
DSM Programs [Member]
Rate And Other Regulatory Matters [Line Items]
South Carolina Commission Order, Annual DSM Program Rate Rider Recovery Amount					$ 48
DSM Programs [Member] | Forecast
Rate And Other Regulatory Matters [Line Items]
South Carolina Commission Order, Annual DSM Program Rate Rider Recovery Amount	$ 43
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%
Retail electric customer balance		$ 15
Welfare charges for customers		15
Due days for forgive retail electric customer balance				60 days
Non fuel base rate increase after amortization		$ 36