Regulatory Matters (Narrative) (Detail) $ in Millions			1 Months Ended																	3 Months Ended						6 Months Ended	9 Months Ended		12 Months Ended
	Nov. 01, 2021 USD ($)	Sep. 01, 2021 USD ($)	Nov. 30, 2021 USD ($)	Oct. 31, 2021 USD ($)	Sep. 30, 2021 USD ($) MW	Aug. 31, 2021 USD ($)	Jul. 31, 2021 USD ($)	Jun. 30, 2021 USD ($) Project Component	May 31, 2021 USD ($)	Apr. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Feb. 28, 2021 USD ($)	Jan. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) program	Sep. 30, 2020 USD ($) mi	Aug. 31, 2020 USD ($)	Jul. 31, 2020 USD ($) MW	Jun. 30, 2020 USD ($)	Apr. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2022 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2008	Dec. 31, 2019 USD ($)
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																				$ (222)				$ 1,151			$ 194	$ 1,963
Other operations and maintenance																				924				977			2,806	2,720
Regulatory assets					$ 10,406									$ 9,832						10,406			$ 9,832			$ 9,832	10,406					$ 9,832
South Carolina Regulation | South Carolina Electric Base Rate Case
Public Utilities General Disclosures [Line Items]
Return of equity percentage																5.90%
Increase (decrease) in revenue requirement							$ 62									$ 178
Increase (decrease) in revenue requirement, percentage																7.75%
Approved return on equity percentage							9.50%									10.25%
Public utilities, requested rate increase amortization of certain excess deferred income taxes							$ 36
Public utilities, retail electric customer balance							15
Public utilities energy efficiency upgrades and critical health and safety repairs							$ 15
Regulatory assets								$ 237													$ 237
South Carolina Regulation | South Carolina Electric Base Rate Case | Impairment of Assets and Other Charges (Benefits)
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																					249
Asset impairment charges after tax																					187
South Carolina Regulation | South Carolina Electric Base Rate Case | Other Income
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																					18
Asset impairment charges after tax																					$ 14
West Virginia Regulation | South Carolina Electric Base Rate Case
Public Utilities General Disclosures [Line Items]
Return of equity percentage															10.25%
Increase in gas cost															$ 28
Approved return on equity percentage							9.54%								9.45%
Approved increase in revenue required							$ 13
Public Utilities distribution infrastructure gathering assets | mi															2,000
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																				(230)				200			(269)	1,008
Proposed cost of project					1,400
Other operations and maintenance																				393				456			1,140	$ 1,083
Regulatory assets					$ 4,631									3,804						4,631			3,804			3,804	4,631					3,804
Virginia Electric and Power Company | Utility Scale Solar Generation
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW					661
Virginia Electric and Power Company | Energy Storage
Public Utilities General Disclosures [Line Items]
Targeted capacity provided by legislation | MW					70
Virginia Electric and Power Company | Subsequent Event
Public Utilities General Disclosures [Line Items]
Proposed cost of project				$ 3,900
Virginia Electric and Power Company | Subsequent Event | CVOW Commercial Project
Public Utilities General Disclosures [Line Items]
Estimated cost			$ 1,100
Approved annual revenue required			$ 79
Virginia Electric and Power Company | Impairment of Assets and Other Charges
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																						$ 76	127		$ 754
Asset impairment charges after tax																						56			$ 561
Virginia Electric and Power Company | GTSA | Impairment of Assets and Other Charges
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																										130
Impairment of assets and other charges (benefits)																						130		200
Impairment of assets and other charges (benefits) after tax																						97		$ 149
Virginia Electric and Power Company | Grassfield Solar Norge Solar And Sycamore Solar
Public Utilities General Disclosures [Line Items]
Proposed cost of project																	$ 170
Targeted capacity provided by legislation | MW																	82
Virginia Electric and Power Company | Virginia Power North Carolina Fuel Filing
Public Utilities General Disclosures [Line Items]
Fuel Component of Electric Rates						$ 26
Virginia Electric and Power Company | Virginia Regulation
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																				318
Virginia Electric and Power Company | Virginia Regulation | Subsequent Event
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement				330
Refund to customer over 6 month period				255
Refund to customer three years				75
Increase (Decrease) Over Previous Year				309
Virginia Electric and Power Company | Virginia Regulation | Impairment of Assets and Other Charges
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																				318
Asset impairment charges after tax																				237
Virginia Electric and Power Company | Virginia Regulation | Operating Revenue
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																				350
Asset impairment charges after tax																				261
Virginia Electric and Power Company | Virginia Regulation | Regulatory Asset Associated with Early Retirements
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																				549
Asset impairment charges after tax																				$ 409
Virginia Electric and Power Company | Virginia Regulation | GTSA
Public Utilities General Disclosures [Line Items]
Number of electric distribution grid transformation projects | Project								14
Number of electric distribution grid transformation projects components | Component								6
Proposed cost of project								$ 669
Other operations and maintenance								110
Virginia Electric and Power Company | Virginia Regulation | Grassfield Solar Norge Solar And Sycamore Solar
Public Utilities General Disclosures [Line Items]
Approved annual revenue required										$ 10
Virginia Power | Mandatory Renewable Portfolio Standard Program
Public Utilities General Disclosures [Line Items]
Proposed cost of project														$ 13
Beginning date of total revenue requirement														Aug. 01, 2021
Approval date														2021-07
Virginia Power | Solar Generation and Energy Storage
Public Utilities General Disclosures [Line Items]
Increase (Decrease) Over Previous Year					$ 61
Proposed cost of project					71
Questar Gas Company | Utah Regulation
Public Utilities General Disclosures [Line Items]
Increase in gas cost									$ 43
Questar Gas Company | Utah Regulation | Subsequent Event
Public Utilities General Disclosures [Line Items]
Increase in gas cost				$ 83
Base Rate Case | Virginia Electric and Power Company | Virginia Regulation
Public Utilities General Disclosures [Line Items]
Return of equity percentage									10.42%		10.85%
CVOWP project investment elected for CCRO to offset available revenues											$ 26
Authorized return percentage											9.20%
Requested authorized return on equity percentage											10.80%
Base Rate Case | Virginia Electric and Power Company | Virginia Regulation | Subsequent Event
Public Utilities General Disclosures [Line Items]
Authorized return percentage				9.35%
Increase (decrease) in revenue requirement				$ 50
Base Rate Case | PSNC
Public Utilities General Disclosures [Line Items]
Authorized return percentage										9.70%
Increase (decrease) in revenue requirement										$ 53
Increase (decrease) in revenue requirement in connection with federal and state income tax reductions										$ 42
Percentage of earned return										10.25%
Base Rate Case | PSNC | Subsequent Event
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement in connection with federal and state income tax reductions, initial rate year				4
Increase (decrease) in revenue requirement in connection with federal and state income tax reductions, second rate year				23
Increase (decrease) in revenue requirement in connection with federal and state income tax reductions, third through fifth rate year				$ 25
Return on equity percentage				9.60%
Increase in gas cost	$ 29
Recovery amount of operation and maintenance costs				$ 106
Recovery period of operation and maintenance costs				4 years
Annual Fuel Factor | Virginia Electric and Power Company | Virginia Regulation
Public Utilities General Disclosures [Line Items]
Total revenue requirement									$ 1,400
Rate year beginning									2021-07
Estimated under-recovered balances									$ 72
Rider U | Virginia Electric and Power Company | Virginia Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement								16										$ 28
Projected capital investment								96										80
Rider U | Virginia Electric and Power Company | Virginia Regulation | Fifth Phase
Public Utilities General Disclosures [Line Items]
Projected capital investment																		36
Rider U | Virginia Electric and Power Company | Virginia Regulation | Previous Phase
Public Utilities General Disclosures [Line Items]
Projected capital investment								61										$ 44
Rider U | Virginia Electric and Power Company | Virginia Regulation | Six Phase
Public Utilities General Disclosures [Line Items]
Projected capital investment								35
Rider CCR | Virginia Electric and Power Company | Virginia Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement												$ 216
Rider T1 | Virginia Electric and Power Company | Virginia Regulation | Operating Segments
Public Utilities General Disclosures [Line Items]
Total revenue requirement									381
Approved annual revenue required									$ 190
Application date									2021-05
Beginning date of total revenue requirement									Sep. 01, 2021
Rider T1 | Virginia Electric and Power Company | Virginia Regulation | Transmission Component Of Virginia Powers | Operating Segments
Public Utilities General Disclosures [Line Items]
Total revenue requirement									$ 493
Rider T1 | Virginia Electric and Power Company | FERC-regulated | Operating Segments
Public Utilities General Disclosures [Line Items]
Total revenue requirement									$ 874
Rider GV | Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement																											21
Total revenue requirement																											$ 153
Rate year beginning																											2021-04
Application date																											2020-06
Rider GV | Virginia Electric and Power Company | Rate Rider One
Public Utilities General Disclosures [Line Items]
Total revenue requirement								$ 142
Beginning date of total revenue requirement								Apr. 01, 2022
Rider GV | Virginia Electric and Power Company | Rate Rider Two
Public Utilities General Disclosures [Line Items]
Total revenue requirement								$ 127
Beginning date of total revenue requirement								Apr. 30, 2023
Rider R | Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement																											$ 14
Total revenue requirement																											$ 58
Rate year beginning																											2021-04
Application date																											2020-06
Rider R | Virginia Electric and Power Company | Rate Rider One
Public Utilities General Disclosures [Line Items]
Total revenue requirement								$ 59
Beginning date of total revenue requirement								Apr. 01, 2022
Rider R | Virginia Electric and Power Company | Rate Rider Two
Public Utilities General Disclosures [Line Items]
Total revenue requirement								$ 55
Beginning date of total revenue requirement								Apr. 01, 2023
Rider S | Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement																											$ (1)
Total revenue requirement																											$ 194
Rate year beginning																											2021-04
Application date																											2020-06
Rider S | Virginia Electric and Power Company | Virginia City Hybrid Energy Center | Rate Rider One
Public Utilities General Disclosures [Line Items]
Total revenue requirement								$ 192
Beginning date of total revenue requirement								Apr. 01, 2022
Rider S | Virginia Electric and Power Company | Virginia City Hybrid Energy Center | Rate Rider Two
Public Utilities General Disclosures [Line Items]
Total revenue requirement								$ 191
Beginning date of total revenue requirement								Apr. 01, 2023
Rider RGGI | Virginia Electric and Power Company | Virginia City Hybrid Energy Center | Rate Rider One
Public Utilities General Disclosures [Line Items]
Approved annual revenue required						$ 168
Beginning date of total revenue requirement						Sep. 01, 2021
Rider GT | Virginia Electric and Power Company | Virginia City Hybrid Energy Center | Rate Rider One
Public Utilities General Disclosures [Line Items]
Approved annual revenue required						$ 56
Beginning date of total revenue requirement						Jun. 01, 2022
Riders C1a C2a And C3a
Public Utilities General Disclosures [Line Items]
Number of new demand response programs | program														1
Riders C1a C2a And C3a | Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Amount of cost recovery														$ 162
Riders C1a C2a And C3a | Virginia Electric and Power Company | Virginia Regulation | 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
Rider C4A | Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Increase (Decrease) Over Previous Year					14
Rider C4A | Virginia Electric and Power Company | Virginia Regulation | Operating Segments | Energy Efficiency Program
Public Utilities General Disclosures [Line Items]
Approved annual revenue required					74
Rider BW Year One | Virginia Electric and Power Company | Virginia Regulation | Subsequent Event | Operating Segments | Energy Efficiency Program
Public Utilities General Disclosures [Line Items]
Approved annual revenue required				$ 145
Rider BW Year Two | Virginia Electric and Power Company | Virginia Regulation | Subsequent Event | Operating Segments | Energy Efficiency Program
Public Utilities General Disclosures [Line Items]
Approved annual revenue required				120
Rider SNA | Virginia Power | Virginia Regulation | Subsequent Event | Nuclear Life Extension Program
Public Utilities General Disclosures [Line Items]
Increase (Decrease) Over Previous Year				109
Approved annual revenue required				1,200
Pipeline Integrity and Safety Program | North Carolina Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement					1
Total revenue requirement					$ 34
Rate year beginning					2021-10
Rider D | PSNC | North Carolina Regulation
Public Utilities General Disclosures [Line Items]
Increase in gas cost					$ 61
Rider DSM | Dominion Energy South Carolina Inc | South Carolina Regulation
Public Utilities General Disclosures [Line Items]
Application date													2021-01
Approval date										2021-04
Annual transportation cost rate adjustment, approval amount requested to recover amount		$ 43											$ 48
Cost of Fuel | Dominion Energy South Carolina Inc | South Carolina Regulation
Public Utilities General Disclosures [Line Items]
Rate year beginning												2021-05
Application date												2021-02
Approval date										2021-04
Increase decrease in annual base fuel component recoveries												$ 36
Gas Rate Case | Dominion Energy South Carolina Inc | South Carolina Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement								$ 9
Total revenue requirement								$ 426
Gas Rate Case | Dominion Energy South Carolina Inc | South Carolina Regulation | Subsequent Event
Public Utilities General Disclosures [Line Items]
Total revenue requirement				424
Approved increase in revenue required				$ 7
PIR Program | Ohio Regulation
Public Utilities General Disclosures [Line Items]
Approved annual revenue required																			$ 243
Percentage of pipeline system replaced																																	25.00%
Total estimated cost														$ 178									178			178						178
Total cumulative estimated cost																			$ 2,000
C E P Program | Ohio Regulation
Public Utilities General Disclosures [Line Items]
Total estimated cost														99									99			99						99		$ 137
Total cumulative estimated cost														$ 957									$ 957			$ 957						957
Proposed revenue requirement										$ 119
UEX Rider | Ohio Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement																						20
Public utilities, under-recovered accumulated bad debt expense																						$ 7
UEX Rider | Ohio Regulation | Scenario Forecast
Public Utilities General Disclosures [Line Items]
Recovery of bad debt expense																														$ 13
PREP
Public Utilities General Disclosures [Line Items]
Rate year beginning									2021-11
Application date									2021-05
PREP | Hope Gas Inc | West Virginia Regulation
Public Utilities General Disclosures [Line Items]
Amount of cost recovery																																$ 34
PREP | Hope Gas Inc | West Virginia Regulation | Scenario Forecast
Public Utilities General Disclosures [Line Items]
Projected capital investment																													$ 56		$ 54
PREP | Hope Gas Inc | West Virginia Regulation | Subsequent Event
Public Utilities General Disclosures [Line Items]
Amount of cost recovery	$ 9