Regulatory Matters (Narrative) (Detail) $ in Millions	1 Months Ended								3 Months Ended	12 Months Ended
	Apr. 30, 2020 USD ($) MW GW	Mar. 31, 2020 USD ($)	Feb. 29, 2020 USD ($)	Jan. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jul. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jul. 31, 2018 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2008	Jan. 31, 2019 USD ($)
Virginia Electric and Power Company | Rider US-3
Public Utilities General Disclosures [Line Items]
Approved cost of project									$ 18
Total annual revenue requirement									$ 28
East Ohio | Pipeline Infrastructure Replacement Program
Public Utilities General Disclosures [Line Items]
Percentage of pipeline system replaced											25.00%
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 | Subsequent Event | East Ohio | Pipeline Infrastructure Replacement Program
Public Utilities General Disclosures [Line Items]
Total annual revenue requirement	$ 218
Total estimated cost	209
Total cumulative estimated cost	$ 1,800
Virginia Regulation | Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Proposed revenue requirement			$ 1,200
Proposed revenue requirement recovered balance			81
Increase (decrease) in revenue requirement		$ (393)
Virginia Regulation | Virginia Electric and Power Company | GTSA
Public Utilities General Disclosures [Line Items]
Estimated cost of project								$ 816				$ 68
Operations and maintenance expenses					$ 78			$ 102
Proposed cost of project					503
Approved cost of project		212
Virginia Regulation | Virginia Electric and Power Company | Solar Development Project | Rider US-3 | Operating Segments
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 | Subsequent Event
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 | Subsequent Event | Virginia Electric and Power Company | 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 Regulation | Subsequent Event | 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 | Subsequent Event | 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 | Subsequent Event | 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 | Subsequent Event | 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 | Subsequent Event | 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 | Subsequent Event | 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 | Subsequent Event | 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 | Subsequent Event | 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
North Carolina Regulation | Virginia Electric and Power Company
Public Utilities General Disclosures [Line Items]
Percentage of earned return							7.52%
Authorized return percentage							9.90%
Return of equity percentage							10.75%
Approved return on equity percentage				9.75%
North Carolina Regulation | Virginia Electric and Power Company | Annual Base Fuel Revenues
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement					$ 24		$ 27
North Carolina Regulation | PSNC | Pipeline Integrity Tracker
Public Utilities General Disclosures [Line Items]
Increase (decrease) in revenue requirement			7
Total annual revenue requirement			28
South Carolina Regulation | Dominion Energy South Carolina Inc
Public Utilities General Disclosures [Line Items]
Annual transportation cost rate adjustment, approval amount requested to recover amount				$ 40
Increase decrease in annual base fuel component recoveries			$ 44
Federal Energy Regulatory Commission | Cove Point | Atlantic Coast Pipeline
Public Utilities General Disclosures [Line Items]
Annual cost-of-service, amount				$ 182
Federal Energy Regulatory Commission | Cove Point | Supply Header Project | Atlantic Coast Pipeline
Public Utilities General Disclosures [Line Items]
Annual transportation cost rate adjustment, approval amount requested to recover amount		$ 28