Regulatory Matters (Narrative) (Detail) $ in Millions		1 Months Ended																9 Months Ended	12 Months Ended
	Nov. 01, 2020 USD ($)	Oct. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) mi	Aug. 31, 2020 USD ($)	Jul. 31, 2020 USD ($) GW	Jun. 30, 2020 USD ($)	May 31, 2020 USD ($) kV	Apr. 30, 2020 USD ($) MW GW	Mar. 31, 2020 USD ($)	Feb. 29, 2020 USD ($) kV mi	Jan. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) a kV ServiceLine mi	Nov. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jul. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jul. 31, 2018 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2008	Jan. 31, 2019 USD ($)
Public Utilities General Disclosures [Line Items]
Number of new demand response programs | a												1
Pipeline Integrity and Safety Program
Public Utilities General Disclosures [Line Items]
Rate year beginning									2020-03
Rider DSM
Public Utilities General Disclosures [Line Items]
Approval date								2020-04
Application date											2020-01
Cost of Fuel
Public Utilities General Disclosures [Line Items]
Rate year beginning										2020-05
Approval date								2020-04
Application date										2020-02
PIR Program
Public Utilities General Disclosures [Line Items]
Percentage of pipeline system replaced																						25.00%
PREP
Public Utilities General Disclosures [Line Items]
Rate year beginning							2020-11
Application date							2020-05
Target to Reach by End of 2025
Public Utilities General Disclosures [Line Items]
Energy efficiency target percentage. based on energy savings from 2019 baseline								5.00%
Virginia Electric and Power Company | Rider US-4
Public Utilities General Disclosures [Line Items]
Total revenue requirement																		$ 12
Rate year beginning																		2021-06
Increase (decrease) in revenue requirement																		$ 4
Application date																		2020-07
Virginia Electric and Power Company | Riders C1A C2A and C3A
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement												$ 11
Amount of cost recovery												186
Virginia Power | Grassfield Solar, Norge Solar and Sycamore Solar
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | GW					82
Proposed cost of project					$ 170
Virginia Power | Grassfield Solar, Norge Solar and Sycamore Solar | Subsequent Event
Public Utilities General Disclosures [Line Items]
Public utilities, projects proposed revenue requirement		$ 11
Dominion Energy South Carolina Inc | Transmission Lines in Aiken County South Carolina
Public Utilities General Disclosures [Line Items]
Estimated cost of project										$ 30
Ohio Regulation
Public Utilities General Disclosures [Line Items]
Contract with customer credits tax reform																					$ 600
Tax Reform Act's impact on its equity return																					19
Ohio Regulation | PIR Program
Public Utilities General Disclosures [Line Items]
Approved annual revenue required								$ 218
Total estimated cost												209									209
Total cumulative estimated cost								$ 1,800
Virginia Regulation
Public Utilities General Disclosures [Line Items]
Percentage of electric energy excluding existing nuclear generation and certain new carbon resources								100.00%
Cap on revenue reductions in the first triennial								$ 50
Virginia Regulation | Virginia Electric and Power Company | Annual Fuel Factor
Public Utilities General Disclosures [Line Items]
Total revenue requirement										$ 1,200
Rate year beginning									2020-05	2020-07
Proposed revenue requirement recovered balance						$ 103				$ 81
Increase (decrease) in revenue requirement									$ (393)
Approval date						2020-06
Virginia Regulation | Virginia Electric and Power Company | Rider T1 | Operating Segments
Public Utilities General Disclosures [Line Items]
Approved annual revenue required							$ 73
Total revenue requirement							$ 529
Approval date							2020-07
Application date							2020-05
Beginning date of total revenue requirement							Sep. 01, 2020
Virginia Regulation | Virginia Electric and Power Company | Riders C1A C2A and C3A | Operating Segments | Energy Efficiency Program
Public Utilities General Disclosures [Line Items]
Approved annual revenue required												$ 60
Number of new energy efficiency programs | a												10
Period for cost cap												5 years
Virginia Regulation | Virginia Electric and Power Company | Rider U
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement						$ 28
Projected capital investment						80
Virginia Regulation | Virginia Electric and Power Company | GTSA
Public Utilities General Disclosures [Line Items]
Proposed cost of project														$ 503
Estimated cost of project																	$ 816						$ 68
Operations and maintenance expenses														78			$ 102
Increase (decrease) in revenue requirement									212
Virginia Regulation | Virginia Electric and Power Company | Transmission Component of Virginia Power's | Rider T1 | Operating Segments
Public Utilities General Disclosures [Line Items]
Total revenue requirement							$ 474
Virginia Regulation | Virginia Electric and Power Company | Fifth Phase | Rider U
Public Utilities General Disclosures [Line Items]
Projected capital investment						36
Virginia Regulation | Virginia Electric and Power Company | Previous Phase | Rider U
Public Utilities General Disclosures [Line Items]
Projected capital investment						44
Virginia Regulation | Virginia Electric and Power Company | Solar and Onshore Wind | Target to Reach by End of 2035
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | GW								16.1
Virginia Regulation | Virginia Electric and Power Company | Utility-scale Solar | Target to Reach by End of 2035 | Maximum
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | GW								15.0
Virginia Regulation | Virginia Electric and Power Company | Utility-scale Solar | Target to Reach by End of 2024
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | GW								3.0
Virginia Regulation | Virginia Electric and Power Company | Small-scale Solar | Target to Reach by End of 2035
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | GW								1.1
Virginia Regulation | Virginia Electric and Power Company | Energy Storage | Target to Reach by End of 2035
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW								2,700
Virginia Regulation | Virginia Electric and Power Company | Offshore Wind Facility | Target to Reach by End of 2035 | Maximum
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW								5,200
Constructed by utility capacity | MW								3,000
Virginia Regulation | Virginia Electric and Power Company | Offshore Wind Facility | Target to Reach by End of 2035 | Minimum
Public Utilities General Disclosures [Line Items]
Constructed by utility capacity | MW								2,500
Virginia Regulation | Virginia Electric and Power Company | Pumped Storage | Target to Reach by End of 2035 | Maximum
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW								800
Virginia Regulation | Virginia Electric and Power Company | Solar Development Project | Rider US-4
Public Utilities General Disclosures [Line Items]
Estimated cost of project															$ 146
Proposed revenue requirement															$ 9
Solar capacity factor when normalized for force majeure events											22.00%
Approved annual revenue required									$ 7
Virginia Regulation | Virginia Electric and Power Company | Electric Transmission Projects | Brambleton-Yardley Ridge line and Brambleton-Poland Road line in Loudoun County, Virginia
Public Utilities General Disclosures [Line Items]
Estimated cost of project												$ 30									30
Capacity of transmission line (kV) | kV												230
Virginia Regulation | Virginia Electric and Power Company | Electric Transmission Projects | Brambleton-Yardley Ridge line
Public Utilities General Disclosures [Line Items]
Estimated cost of project							$ 25
Capacity of transmission line (kV) | kV							230
Federal Energy Regulatory Commission | Virginia Electric and Power Company | Operating Segments
Public Utilities General Disclosures [Line Items]
Total revenue requirement							$ 1,000
North Carolina Regulation | Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement				$ 15
Approved return on equity percentage											9.75%
North Carolina Regulation | Virginia Electric and Power Company | Base Rate Case
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement														$ 24		$ 27
Percentage of earned return																7.52%
Authorized return percentage																9.90%
Return of equity percentage																10.75%
North Carolina Regulation | PSNC | Pipeline Integrity and Safety Program
Public Utilities General Disclosures [Line Items]
Total revenue requirement										28
Increase (decrease) in revenue requirement										7
South Carolina Regulation | Gas Rate Case
Public Utilities General Disclosures [Line Items]
Total revenue requirement						$ 409
Increase (decrease) in revenue requirement																		$ 9
Return of equity percentage						10.25%
Authorized return percentage						9.90%
South Carolina Regulation | Subsequent Event | Gas Rate Case
Public Utilities General Disclosures [Line Items]
Total revenue requirement		406
Increase (decrease) in revenue requirement		$ 6
South Carolina Regulation | South Carolina Electric Base Rate Case
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement				$ 178
Return of equity percentage				5.90%
Approved return on equity percentage				10.25%
Increase (decrease) in revenue requirement, percentage				7.75%
South Carolina Regulation | Dominion Energy South Carolina Inc | Rider DSM
Public Utilities General Disclosures [Line Items]
Annual transportation cost rate adjustment, approval amount requested to recover amount											$ 40
South Carolina Regulation | Dominion Energy South Carolina Inc | Cost of Fuel
Public Utilities General Disclosures [Line Items]
Increase decrease in annual base fuel component recoveries										$ 44
South Carolina Regulation | Dominion Energy South Carolina Inc | Transmission Lines in Aiken County South Carolina
Public Utilities General Disclosures [Line Items]
Capacity of transmission line (kV) | kV										230
Length of kV line (miles | mi										28
South Carolina Regulation | Dominion Energy South Carolina Inc | Scenario Forecast
Public Utilities General Disclosures [Line Items]
Estimated cost of project																				$ 75
West Virginia Regulation | South Carolina Electric Base Rate Case
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement			$ 28
Return of equity percentage			10.25%
Approved return on equity percentage			9.45%
Public Utilities distribution infrastructure gathering assets | mi			2,000
West Virginia Regulation | Hope Gas, Inc. | PREP
Public Utilities General Disclosures [Line Items]
Amount of cost recovery																					$ 27
West Virginia Regulation | Hope Gas, Inc. | Scenario Forecast | PREP
Public Utilities General Disclosures [Line Items]
Amount of cost recovery	$ 13
Projected capital investment																			$ 54	$ 39
Utah Regulation | Rural Expansion Project
Public Utilities General Disclosures [Line Items]
Public utilities, high-pressure pipeline | mi												11
Public utilities, number of service pipeline | ServiceLine												360
Wyoming Base Rate Case | Questar Gas
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement																		$ 2
Return of equity percentage													10.50%
Approved return on equity percentage																		9.35%
Authorized return percentage													9.50%
Base fuel cost													$ 4
Percentage of earned return													7.46%