Regulatory Matters (Narrative) (Detail) MMcf in Millions															1 Months Ended																				3 Months Ended		12 Months Ended
	Feb. 01, 2020 USD ($) mi	Jan. 01, 2020	Nov. 30, 2019	Nov. 01, 2019 USD ($)	Sep. 30, 2019 USD ($)	Aug. 31, 2019 USD ($)	May 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Feb. 01, 2019 USD ($)	Jan. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Nov. 30, 2018 USD ($) mi MW	Nov. 01, 2018 USD ($)	Nov. 30, 2013 mi kV	Mar. 31, 2020 USD ($)	Feb. 29, 2020 USD ($) kV	Jan. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) a	Nov. 30, 2019 USD ($)	Oct. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Aug. 31, 2019 USD ($)	Jul. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	May 31, 2019 USD ($)	Apr. 30, 2019 MMcf	Mar. 31, 2019 USD ($)	Jan. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Oct. 31, 2018 USD ($)	Aug. 31, 2018 USD ($) a	Jul. 31, 2018 USD ($) a	May 31, 2017 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Aug. 31, 2018 USD ($) a	Dec. 31, 2017 USD ($)	Dec. 31, 2011
Public Utilities General Disclosures [Line Items]
Reduction in regulatory liabilities																																							$ 35,000,000		$ 4,200,000,000
Proposed revenue requirement																																						$ 83,000,000
Increase (decrease) in revenue requirement																		$ 11
Number of new demand response programs | a																		1
Amount of cost recovery																		$ 186
Public utilities length of wind project | mi												27
Actual cumulative PREP Investment											$ 723,000,000																		$ 723,000,000							$ 723,000,000			723,000,000
Impairment of assets and other charges																																						$ 1,535,000,000	403,000,000		15,000,000
Agreement to provide Dths per day of transportation service | a																															150,000									150,000
Base fuel cost							$ 35,000,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
DETI
Public Utilities General Disclosures [Line Items]
The total estimated capital investment																		$ 25,000,000																				$ 25,000,000
Scenario, Forecast
Public Utilities General Disclosures [Line Items]
Increase decrease in annual base fuel component recoveries																$ 44,000,000
North Carolina Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement											13,000,000
Return of equity percentage		9.75%
Ohio Regulation
Public Utilities General Disclosures [Line Items]
Projected capital investment																																							$ 200,000,000
Return of equity percentage																																							3.00%
Contract with customer credits taxreform																																						600,000,000
South Carolina Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement													$ (20,000,000)
Wyoming Base Rate Case
Public Utilities General Disclosures [Line Items]
Return of equity percentage																							10.50%
Percentage of earned return																							9.05%
Authorized return percentage																							9.85%
Wyoming Base Rate Case | Scenario, Forecast | Annual Base Fuel Revenues
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement															$ 19,000,000
Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Tax reform benefit																															$ 100,000,000								$ 100,000,000
Reduction in regulatory liabilities																																							31,000,000		2,600,000,000
Impairment of assets and other charges																												$ 160,000,000										$ 757,000,000
Submitted and approved decrease in base rate revenue																														$ 14,000,000
Regulatory liabilities one time bill credit reduction amount																																			$ 13,000,000
Return of equity percentage			9.20%
Virginia Electric and Power Company | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Virginia Electric and Power Company | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Virginia Electric and Power Company | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Virginia Electric and Power Company | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Virginia Electric and Power Company | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Virginia Electric and Power Company | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Virginia Electric and Power Company | Rider E
Public Utilities General Disclosures [Line Items]
Total revenue requirement																																						$ 88,000,000
Increase (decrease) in revenue requirement																																						(16,000,000)
Virginia Electric and Power Company | Federal Energy Regulatory Commission | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement																									$ 920,000,000
Virginia Electric and Power Company | Virginia Regulation
Public Utilities General Disclosures [Line Items]
Proposed annual revenue reduction amount								$ 183,000,000																				171,000,000
Annual revenue reduction amount																											$ 183,000,000
Estimated annual revenue reduction on one-time customer credit																																			132,000,000
Interim rate reduction amount																																$ 125,000,000
Rate reduction	$ 67,000,000								$ 63,000,000
One-time bill credit, provisions for current customers																																						200,000,000
Charge associated with legislation																																						215,000,000
Charge associated with legislation, after tax																																						160,000,000
Legislation amount credited in customer bill																												$ 77,000,000				138,000,000
Proposed revenue requirement																1,200,000,000									1,500,000,000
Increase (decrease) in revenue requirement																(393,000,000)								$ 254,000,000	192,000,000
Return of equity percentage																											10.75%
Proposed revenue requirement recovered balance																81,000,000								107,000,000	124,000,000
Virginia Electric and Power Company | Virginia Regulation | Transmission Component of Virginia Power's | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement																									474,000,000
Virginia Electric and Power Company | Virginia Regulation | Coastal Virginia Offshore Wind Project
Public Utilities General Disclosures [Line Items]
The total estimated capital investment												$ 300,000,000
Capacity of wind turbine generators | MW												6
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 | GTSA
Public Utilities General Disclosures [Line Items]
Operations and maintenance expenses																					$ 78,000,000																	102,000,000
Proposed cost of project																					503,000,000
Estimated Cost of project										$ 68,000,000																												816,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider T1 | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement																									446,000,000
Increase (decrease) in revenue requirement																							$ 146,000,000		$ 271,000,000
Virginia Electric and Power Company | Virginia Regulation | Riders C1A C2A and C3A | Energy Efficiency Program | Operating Segments
Public Utilities General Disclosures [Line Items]
Approved revenue required																		$ 60
Number of new energy efficiency programs | a																		10
Period for cost cap																		5 years
Virginia Electric and Power Company | Virginia Regulation | Rider E
Public Utilities General Disclosures [Line Items]
Approved revenue required																													114,000,000									104,000,000
Virginia Electric and Power Company | Virginia Regulation | Rider E | Other operations and maintenance
Public Utilities General Disclosures [Line Items]
Audit compliance charge recognized in connection with preliminary recommendation																																						21,000,000
Audit compliance after-tax charge recognized in connection with preliminary recommendation																																						16,000,000
Virginia Electric and Power Company | Virginia Regulation | Solar Development Project
Public Utilities General Disclosures [Line Items]
The total estimated capital investment																																$ 410,000,000
Number of solar facility | a																																2
Virginia Electric and Power Company | Virginia Regulation | Solar Development Project | Rider US-3
Public Utilities General Disclosures [Line Items]
Solar capacity factor when normalized for force majeure events										25.00%
Virginia Electric and Power Company | Virginia Regulation | Solar Development Project | Rider US-3 | Operating Segments
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement																							$ 9,000,000									$ 10,000,000
Virginia Electric and Power Company | Virginia Regulation | Solar Development Project | Rider US-3 | Operating Segments | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities										20 years																		20 years
Virginia Electric and Power Company | Virginia Regulation | Solar Development Project | Rider US-3 | Operating Segments | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																	20 years
Virginia Electric and Power Company | Virginia Regulation | Battery Storage Pilot
Public Utilities General Disclosures [Line Items]
Estimated Cost of project						$ 35,000,000
Virginia Electric and Power Company | Virginia Regulation | Maximum
Public Utilities General Disclosures [Line Items]
Rate reduction																																						$ 50,000,000
Virginia Electric and Power Company | Virginia Regulation | Subsequent Event | Solar Development Project | Rider US-3 | Operating Segments
Public Utilities General Disclosures [Line Items]
Solar capacity factor when normalized for force majeure events																	22.00%
Virginia Electric and Power Company | Virginia Regulation | Third Phase | Rider U
Public Utilities General Disclosures [Line Items]
Projected capital investment																				$ 123,000,000
Virginia Electric and Power Company | Virginia Regulation | Second Phase | Rider U
Public Utilities General Disclosures [Line Items]
Projected capital investment																				52,000,000
Virginia Electric and Power Company | North Carolina Regulation
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement						$ 18,000,000
Return of equity percentage								10.75%
Percentage of earned return								7.52%
Authorized return percentage								9.90%
Virginia Electric and Power Company | North Carolina Regulation | Annual Base Fuel Revenues
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement				$ 27,000,000	$ 24,000,000
DETI
Public Utilities General Disclosures [Line Items]
Expected cost of project																																								$ 95,000,000
DETI | Federal Energy Regulatory Commission | Supply Header Project | Atlantic Coast Pipeline
Public Utilities General Disclosures [Line Items]
Annual electric power cost rate adjustment, approval amount requested to recover amount																					10,000,000
Annual transportation cost rate adjustment, approval amount requested to recover amount																					$ 38,000,000
DETI | Federal Energy Regulatory Commission | Preliminary recommendation one | Other operations and maintenance
Public Utilities General Disclosures [Line Items]
Audit compliance charge recognized in connection with preliminary recommendation																																							129,000,000
Audit compliance after-tax charge recognized in connection with preliminary recommendation																																							94,000
Questar Gas
Public Utilities General Disclosures [Line Items]
Return of equity percentage	9.50%
Base fuel cost																			$ 4,000,000
Questar Gas | Cost-of-service impact of 2017 Tax Reform Act
Public Utilities General Disclosures [Line Items]
Reduction in regulatory liabilities																																	$ 15,000,000
Refund to customers related to deferred corporate income tax reduction																																$ 9,000,000
Questar Gas | Utah Regulation [Member]
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement	$ 3,000,000
Questar Gas | Utah and Wyoming Regulation | Fuel Deferral
Public Utilities General Disclosures [Line Items]
LNG storage facility, liquefaction rate per day | MMcf																										8.2
Questar Gas | Wyoming Base Rate Case
Public Utilities General Disclosures [Line Items]
Return of equity percentage																																						10.50%
Percentage of earned return																																						7.46%
Authorized return percentage																																						9.50%
East Ohio
Public Utilities General Disclosures [Line Items]
Percentage of debt rate of pipeline system																																										6.50%
East Ohio | Ohio Regulation | Pipeline Infrastructure Replacement Program
Public Utilities General Disclosures [Line Items]
Total revenue requirement																																						$ 190,000,000
Total estimated cost											202,000,000							$ 1,600,000											202,000,000							202,000,000		1,600,000	202,000,000
Hope Gas, Inc. | PREP
Public Utilities General Disclosures [Line Items]
Projected capital investment																																						29,000,000
Hope Gas, Inc. | Scenario, Forecast | PREP
Public Utilities General Disclosures [Line Items]
Projected capital investment																																					$ 39,000,000
Hope Gas, Inc. | West Virginia Regulation | PREP
Public Utilities General Disclosures [Line Items]
Amount of cost recovery																			$ 10,000,000																				30,000,000
Cove Point | Federal Energy Regulatory Commission
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement																						$ 1,000,000
Annual transportation cost rate adjustment, approval amount requested to recover amount																	$ 182,000,000					$ 25,000,000
Estimated Cost of project																																							45,000,000
Impairment of assets and other charges																																							37,000,000
Asset impairment after tax charge											$ 28,000,000																		$ 28,000,000							28,000,000			28,000,000
Cove Point | Federal Energy Regulatory Commission | Supply Header Project | Atlantic Coast Pipeline
Public Utilities General Disclosures [Line Items]
Annual transportation cost rate adjustment, approval amount requested to recover amount																											$ 24,000,000
Public utilities expected cost to acquire productive assets																																		$ 150,000,000
Dominion Energy South Carolina Inc | Scenario, Forecast
Public Utilities General Disclosures [Line Items]
Electric transmission projects Costs	$ 75,000,000
Dominion Energy South Carolina Inc | Scenario, Forecast | Transmission Lines in Aiken County South Carolina
Public Utilities General Disclosures [Line Items]
Electric transmission projects Costs																$ 30,000,000
Dominion Energy South Carolina Inc | Virginia 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
Public Utilities General Disclosures [Line Items]
Total revenue requirement																								437,000,000
Approved revenue required																				$ 436,000,000
Annual transportation cost rate adjustment, approval amount requested to recover amount																	$ 40,000,000
Increase in natural gas rate																																						7,000,000
Dominion Energy Gas Holdings, LLC
Public Utilities General Disclosures [Line Items]
Reduction in regulatory liabilities																																							(8,000,000)		1,100,000,000
Impairment of assets and other charges																																				$ 219,000,000		$ 13,000,000	$ 163,000,000		$ 15,000,000
Dominion Energy Gas Holdings, LLC | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Dominion Energy Gas Holdings, LLC | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Dominion Energy Gas Holdings, LLC | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Dominion Energy Gas Holdings, LLC | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Dominion Energy Gas Holdings, LLC | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Dominion Energy Gas Holdings, LLC | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Public Utilities General Disclosures [Line Items]
Performance guarantee of the facilities																		1 year																				1 year
Dominion Energy Gas Holdings, LLC | Federal Energy Regulatory Commission | Supply Header Project | Subsidiaries
Public Utilities General Disclosures [Line Items]
Impairment of assets and other charges																																			13,000,000
Asset impairment after tax charge																								$ 10,000,000											$ 10,000,000
Ohio Regulation
Public Utilities General Disclosures [Line Items]
Tax Reform Act's impact on its equity return																		$ 19,000,000