Regulatory Matters (Narrative) (Detail) $ in Millions			1 Months Ended																									3 Months Ended	12 Months Ended						13 Months Ended
	Nov. 01, 2020 USD ($)	Nov. 01, 2018 USD ($)	Feb. 25, 2021 USD ($)	Jan. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) program MW	Nov. 30, 2020 USD ($)	Oct. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) mi	Aug. 31, 2020 USD ($)	Jul. 31, 2020 USD ($) MW	Jun. 30, 2020 USD ($)	May 31, 2020 USD ($) kV	Apr. 30, 2020 USD ($) MW	Mar. 31, 2020 USD ($)	Feb. 29, 2020 USD ($) kV mi	Jan. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) program kV ServiceLine mi	Nov. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	May 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jan. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Aug. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Nov. 30, 2013 kV mi	Dec. 31, 2011	Jun. 30, 2019 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2008	Jan. 31, 2019 USD ($)
Public Utilities General Disclosures [Line Items]
Impairment of assets and other charges																														$ 2,105	$ 1,520	$ 12
Actual cumulative PREP Investment					$ 721																		$ 723							721		$ 723
Proposed revenue requirement					$ 83																									83
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%
Impairment of Assets and Other Charges
Public Utilities General Disclosures [Line Items]
Impairment of assets and other charges																			$ 26
Impairment of assets and other charges after tax																			19
Riders C1a C2a And C3a
Public Utilities General Disclosures [Line Items]
Number of new demand response programs | program																	1
Rider C4A
Public Utilities General Disclosures [Line Items]
Number of new demand response programs | program					1
Pipeline Integrity and Safety Program
Public Utilities General Disclosures [Line Items]
Rate year beginning								2020-09
Pipeline Integrity and Safety Program | Subsequent Event
Public Utilities General Disclosures [Line Items]
Rate year beginning			2021-03
Rider D S M
Public Utilities General Disclosures [Line Items]
Application date																2020-01
Rider D S M | Subsequent Event
Public Utilities General Disclosures [Line Items]
Application date				2021-01
PREP
Public Utilities General Disclosures [Line Items]
Rate year beginning												2020-11
Application date												2020-05
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 | Brambleton-Yardley Ridge line and Brambleton-Poland Road line in Loudoun County, Virginia | Electric Transmission Projects
Public Utilities General Disclosures [Line Items]
Anticipated projected cost																	$ 30														30
Capacity of transmission line (kV) | kV																	230
Virginia Regulation | Brambleton-Yardley Ridge line | Electric Transmission Projects
Public Utilities General Disclosures [Line Items]
Anticipated projected cost												$ 25
Capacity of transmission line (kV) | kV												230
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]
Return of equity percentage					3.00%																											3.00%
Approved annual revenue required													218
Projected capital investment																																$ 200
Period for cost cap					5 years
Percentage of pipeline system replaced																																		25.00%
Total estimated cost																	$ 209														209
Total cumulative estimated cost													$ 1,800
Last date of investment					Dec. 31, 2026
South Carolina Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement		$ (20)
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 | Gas Rate Case
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement							$ 6				$ 9
Return of equity percentage											10.25%
Total revenue requirement							406				$ 409
Authorized return percentage											9.90%
North Carolina Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement																							$ (13)
North Carolina Regulation | Pipeline Integrity and Safety Program
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement								$ 3
Total revenue requirement								31
North Carolina Regulation | Pipeline Integrity and Safety Program | Subsequent Event
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement			$ 2
Total revenue requirement			$ 33
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
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
DETI | FERC-regulated | Preliminary recommendation one | Discontinued Operations
Public Utilities General Disclosures [Line Items]
Audit compliance charge recognized in connection with preliminary recommendation																																129
Audit compliance after-tax charge recognized in connection with preliminary recommendation																																94
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Tax reform benefit																								$ 100											$ 100
Submitted and approved increase (decrease) in base rate revenue																					$ 14
Regulatory liabilities one time bill credit reduction amount																												$ 13
Return of equity percentage																		9.20%
Impairment of assets and other charges																														1,093	757
Virginia Electric and Power Company | Income Payment Program
Public Utilities General Disclosures [Line Items]
Total revenue requirement					$ 93
Virginia Electric and Power Company | Impairment of Assets and Other Charges
Public Utilities General Disclosures [Line Items]
Impairment of assets and other charges						$ 127								$ 751					17	$ 62	346	$ 160								130
Impairment of assets and other charges after tax						$ 94								559					12	$ 46	257	119								97
Virginia Electric and Power Company | Riders C1a C2a And C3a
Public Utilities General Disclosures [Line Items]
Submitted and approved increase (decrease) in base rate revenue																	$ 11
Amount of cost recovery																	186
Virginia Electric and Power Company | Rider C4A
Public Utilities General Disclosures [Line Items]
Submitted and approved increase (decrease) in base rate revenue					18
Amount of cost recovery					162
Virginia Electric and Power Company | FERC-regulated | Operating Segments
Public Utilities General Disclosures [Line Items]
Total revenue requirement												$ 1,000
Virginia Electric and Power Company | Virginia Regulation
Public Utilities General Disclosures [Line Items]
Annual revenue reduction amount																					183
Estimated annual revenue reduction on one-time customer credit																												$ 132
Rate reduction																														66	63
One-time bill credit, provisions for current customers																																	$ 200
Charge associated with legislation																																215
Charge associated with legislation, after tax																																$ 160
Legislation amount credited in customer bill																						$ 77			$ 138
Public Utilities Interim Rate Reduction Amount																									$ 125
Proposed annual revenue reduction amount																					183
Virginia Electric and Power Company | Virginia Regulation | GTSA
Public Utilities General Disclosures [Line Items]
Submitted and approved increase (decrease) in base rate revenue														212
Projects plan period																						10 years
Period of petition filed for projects approval																						3 years
Anticipated projected cost																						$ 68													$ 68
Proposed cost of project																			503
Operations and maintenance expenses																			78
Virginia Electric and Power Company | Virginia Regulation | Surry Switching Station Transmission Line
Public Utilities General Disclosures [Line Items]
Length of kV line (miles) | mi																										7
Capacity of transmission line (kV) | kV																										500
Virginia Electric and Power Company | Virginia Regulation | Transmission Line from Skiffes Creek Switching Station to Wheaton Substation
Public Utilities General Disclosures [Line Items]
Length of kV line (miles) | mi																										20
Virginia Electric and Power Company | Virginia Regulation | Transmission Line Near Gainesville Substation And Haymarket Substation
Public Utilities General Disclosures [Line Items]
Capacity of transmission line (kV) | kV																										230
Virginia Electric and Power Company | Virginia Regulation | Forecast
Public Utilities General Disclosures [Line Items]
Rate reduction																													$ 50
Virginia Electric and Power Company | Virginia Regulation | Target to Reach by End of 2035 | Solar And Onshore Wind
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW													16,100
Virginia Electric and Power Company | Virginia Regulation | Target to Reach by End of 2035 | Utility-scale Solar | Maximum
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW													15,000.0
Virginia Electric and Power Company | Virginia Regulation | Target to Reach by End of 2035 | Small-scale Solar
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW													1,100
Virginia Electric and Power Company | Virginia Regulation | Target to Reach by End of 2035 | Energy Storage
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW													2,700
Virginia Electric and Power Company | Virginia Regulation | Target to Reach by End of 2035 | Pumped Storage | Maximum
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW													800
Virginia Electric and Power Company | Virginia Regulation | Target to Reach by End of 2035 | Offshore Wind Facility | Maximum
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW													5,200
Constructed by utility capacity | MW													3,000.0
Virginia Electric and Power Company | Virginia Regulation | Target to Reach by End of 2035 | Offshore Wind Facility | Minimum
Public Utilities General Disclosures [Line Items]
Constructed by utility capacity | MW													2,500
Virginia Electric and Power Company | Virginia Regulation | Target to Reach by End of 2024 | Utility-scale Solar
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW													3,000.0
Virginia Electric and Power Company | Virginia Regulation | Annual Fuel Factor
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement														$ (393)
Total revenue requirement															$ 1,200
Rate year beginning														2020-05	2020-07
Proposed revenue requirement recovered balance											$ 103				$ 81
Approval date											2020-06
Virginia Electric and Power Company | Virginia Regulation | Rider T1 | Operating Segments
Public Utilities General Disclosures [Line Items]
Total revenue requirement												$ 529
Approval date												2020-07
Approved annual revenue required												$ 73
Application date												2020-05
Beginning date of total revenue requirement												Sep. 01, 2020
Virginia Electric and Power Company | Virginia Regulation | Rider T1 | Transmission Component Of Virginia Powers | Operating Segments
Public Utilities General Disclosures [Line Items]
Total revenue requirement												$ 474
Virginia Electric and Power Company | Virginia Regulation | Rider U
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement											$ 28
Projected capital investment											80
Virginia Electric and Power Company | Virginia Regulation | Rider U | Fifth Phase
Public Utilities General Disclosures [Line Items]
Projected capital investment											36
Virginia Electric and Power Company | Virginia Regulation | Rider U | Previous Phase
Public Utilities General Disclosures [Line Items]
Projected capital investment											44
Virginia Electric and Power Company | Virginia Regulation | 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 | program																	10
Period for cost cap																	5 years
Virginia Electric and Power Company | Virginia Regulation | Rider C4A | Operating Segments | Energy Efficiency Program
Public Utilities General Disclosures [Line Items]
Approved annual revenue required					$ 78
Number of new energy efficiency programs | program					10
Period for cost cap					5 years
Virginia Electric and Power Company | North Carolina Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement									$ (16)
Approved return on equity percentage																9.75%
Virginia Electric and Power Company | North Carolina Regulation | Base Rate Case
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement																			$ 24		$ 27
Return of equity percentage																					10.75%
Percentage of earned return																					7.52%
Authorized return percentage																					9.90%
Virginia Power | Grassfields Solar Norge Solar And Sycamore Solar
Public Utilities General Disclosures [Line Items]
Proposed cost of project							$ 11			$ 170
Targeted capacity provided by legislation | MW										82
Virginia Power | Fountain Creek Solar and Otter Creek Solar
Public Utilities General Disclosures [Line Items]
Proposed cost of project					$ 280
Targeted capacity provided by legislation | MW					140
Virginia Power | Market Based Carbon Trading Program
Public Utilities General Disclosures [Line Items]
Proposed cost of project					$ 167
Virginia Power | Mandatory Renewable Portfolio Standard Program
Public Utilities General Disclosures [Line Items]
Proposed cost of project					$ 13
Dominion Energy South Carolina Inc | Subsequent Event
Public Utilities General Disclosures [Line Items]
Rate year beginning			2021-05
Increase decrease in annual base fuel component recoveries			$ 36
Dominion Energy South Carolina Inc | Transmission Lines in Aiken County South Carolina
Public Utilities General Disclosures [Line Items]
Estimated cost of project															$ 30
Dominion Energy South Carolina Inc | South Carolina Regulation
Public Utilities General Disclosures [Line Items]
Estimated cost of project																														75
Dominion Energy South Carolina Inc | South Carolina Regulation | Transmission Lines in Aiken County South Carolina
Public Utilities General Disclosures [Line Items]
Length of kV line (miles) | mi															28
Capacity of transmission line (kV) | kV															230
Dominion Energy South Carolina Inc | South Carolina Regulation | Rider D S M
Public Utilities General Disclosures [Line Items]
Annual transportation cost rate adjustment, approval amount requested to recover amount																$ 40
Dominion Energy South Carolina Inc | South Carolina Regulation | Rider D S M | Subsequent Event
Public Utilities General Disclosures [Line Items]
Annual transportation cost rate adjustment, approval amount requested to recover amount				$ 48
Dominion Energy South Carolina Inc | South Carolina Regulation | Cost of Fuel
Public Utilities General Disclosures [Line Items]
Rate year beginning															2020-05
Increase decrease in annual base fuel component recoveries															$ 44
East Ohio
Public Utilities General Disclosures [Line Items]
Percentage of debt rate of pipeline system																											6.50%
Hope Gas Inc | West Virginia Regulation | PREP
Public Utilities General Disclosures [Line Items]
Projected capital investment																														$ 39
Amount of cost recovery	$ 13																														$ 27
Hope Gas Inc | West Virginia Regulation | PREP | Forecast
Public Utilities General Disclosures [Line Items]
Projected capital investment																													$ 54
Questar Gas Company | Utah Regulation
Public Utilities General Disclosures [Line Items]
Increase in gas cost								$ 40
Questar Gas Company | Wyoming Base Rate Case
Public Utilities General Disclosures [Line Items]
Submitted and approved increase (decrease) in base rate revenue											$ 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%