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Quarterly Financial and Common Stock Data (Unaudited) (Narrative) (Detail) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Parent Company Only Financial Information [Line Items]                  
After-tax gains from the sale of certain merchant generation facilities       $ 536          
After-tax impairment charge for certain gathering and processing assets       $ 164          
After-tax charge for disallowance of FERC-regulated plant         $ 89        
After-taxcharge associated with Virginia legislation           $ 160      
SCANA [Member]                  
Parent Company Only Financial Information [Line Items]                  
Gain loss on investments held in nuclear decommissioning trust funds             $ 150    
Charge related to a voluntary retirement program after tax   $ 316              
Charge Related To Litigation Acquired After Tax $ 244 75 $ 134            
Charge related to a contract termination after tax.   100              
Charge For Refunds Collected From Customers     756            
After tax charge for decommissioning costs     197            
After tax charge for closure costs     84            
Merger and integration-related costs     1,300       484    
Virginia Electric and Power Company                  
Parent Company Only Financial Information [Line Items]                  
After-taxcharge associated with Virginia legislation           $ 160      
Gain loss on contract termination   100              
Voluntary retirement expenses after tax   144              
Project abandonement costs after tax   47              
After tax charge for charge for the planned early retirement 409                
After tax charge for closure costs 84                
Virginia Electric and Power Company | SCANA [Member]                  
Parent Company Only Financial Information [Line Items]                  
After tax charge for charge for the planned early retirement     409            
Dominion Energy Gas Holdings, LLC                  
Parent Company Only Financial Information [Line Items]                  
After-tax gains from the sale of certain merchant generation facilities $ 165                
After-tax charge for disallowance of FERC-regulated plant   89              
Voluntary retirement expenses after tax   58              
Merger and integration-related costs             $ 603 $ 230 $ 239
Dominion Energy Gas Holdings, LLC | Discontinued Operations                  
Parent Company Only Financial Information [Line Items]                  
Voluntary retirement expenses after tax   $ 32              
Dominion Energy Gas Holdings, LLC | SCANA [Member]                  
Parent Company Only Financial Information [Line Items]                  
After tax charge for regulatory assets     $ 277