Regulatory Matters (Narrative) (Detail) $ in Millions			1 Months Ended													3 Months Ended					6 Months Ended			12 Months Ended
	Nov. 01, 2021 USD ($)	Sep. 01, 2021 USD ($)	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 ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) mi	Aug. 31, 2020 USD ($)	Jul. 31, 2020 USD ($) MW	Jun. 30, 2020 USD ($)	Apr. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jun. 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																$ 321			$ 44		$ 416		$ 812
Other operations and maintenance																895			852		1,882		1,743
Regulatory assets				$ 9,636						$ 9,832						9,636		$ 9,832			9,636	$ 9,832					$ 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												$ 178
Increase (decrease) in revenue requirement, percentage												7.75%
Approved return on equity percentage												10.25%
Regulatory assets				237												237					237
South Carolina Regulation | South Carolina Electric Base Rate Case | Subsequent Event
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement			$ 62
Approved return on equity percentage			9.50%
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
South Carolina Regulation | South Carolina Electric Base Rate Case | Impairment of Assets and Other Charges
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																249			18		249		18
Impairment of assets and other charges after tax																					187		14
West Virginia Regulation | South Carolina Electric Base Rate Case
Public Utilities General Disclosures [Line Items]
Return of equity percentage											10.25%
Approved return on equity percentage											9.45%
Increase in gas cost											$ 28
Public Utilities distribution infrastructure gathering assets | mi											2,000
West Virginia Regulation | South Carolina Electric Base Rate Case | Subsequent Event
Public Utilities General Disclosures [Line Items]
Approved return on equity percentage			9.54%
Approved increase in revenue required			$ 13
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																12			44		(39)		808
Other operations and maintenance																321			$ 296		747		$ 627
Regulatory assets				$ 3,916						3,804						$ 3,916		3,804			3,916	3,804					3,804
Virginia Electric and Power Company | Impairment of Assets and Other Charges
Public Utilities General Disclosures [Line Items]
Asset net impairment charge																	$ 76	127		$ 754
Impairment of assets and other 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
Benefit in impairment of assets and other charges																	130
Benefit in impairment of assets and other charges after tax																	97
Virginia Electric and Power Company | Grassfields 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 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 | Grassfields 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
Questar Gas Company | Utah Regulation
Public Utilities General Disclosures [Line Items]
Increase in gas cost					$ 43
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 | 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%
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]
Projected capital investment				96										$ 80
Increase (decrease) in revenue requirement				16										28
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]
Total revenue requirement																					$ 153
Rate year beginning																					2021-04
Increase (decrease) in revenue requirement																					$ 21
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]
Total revenue requirement																					$ 58
Rate year beginning																					2021-04
Increase (decrease) in revenue requirement																					$ 14
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]
Total revenue requirement																					$ 194
Rate year beginning																					2021-04
Increase (decrease) in revenue requirement																					$ (1)
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 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									$ 48
Rider DSM | Dominion Energy South Carolina Inc | South Carolina Regulation | Scenario Forecast
Public Utilities General Disclosures [Line Items]
Annual transportation cost rate adjustment, approval amount requested to recover amount		$ 43
Cost of Fuel
Public Utilities General Disclosures [Line Items]
Rate year beginning								2021-05
Application date								2021-02
Approval date															2021-04
Cost of Fuel | Dominion Energy South Carolina Inc | South Carolina Regulation
Public Utilities General Disclosures [Line Items]
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]
Total revenue requirement				$ 426
Increase (decrease) in revenue requirement				$ 9
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
Amount of cost recovery	$ 9