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Business Acquisitions and Dispositions - Narrative (Details) - USD ($)
$ in Millions
1 Months Ended 12 Months Ended
Nov. 06, 2019
Nov. 30, 2020
Jul. 31, 2020
Jun. 30, 2015
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Iroquois Gas Transmission System L.P. [Member]              
Business Acquisition [Line Items]              
Equity method investment, ownership percentage         50.00%    
Eastern Energy Gas Holdings, LLC [Member]              
Business Acquisition [Line Items]              
Contributions         $ 1,223 $ 3,385 $ 48
Noncontrolling Interest, Increase from Sale of Parent Equity Interest             4
Eastern Energy Gas Holdings, LLC [Member] | Noncontrolling Interest [Member]              
Business Acquisition [Line Items]              
Noncontrolling Interest, Increase from Sale of Parent Equity Interest             $ 4
Eastern Energy Gas Holdings, LLC [Member] | Cove Point LNG, LP [Member]              
Business Acquisition [Line Items]              
Noncontrolling interest distributed     25.00%        
Ownership interest       75.00%      
Eastern Energy Gas Holdings, LLC [Member] | White River Hub, LLC [Member]              
Business Acquisition [Line Items]              
Ownership interest       50.00%      
Eastern Energy Gas Holdings, LLC [Member] | Iroquois Gas Transmission System L.P. [Member]              
Business Acquisition [Line Items]              
Ownership interest       25.93%      
Eastern Energy Gas Holdings, LLC [Member] | GT&S Transaction [Member] | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations [Member] | Cove Point LNG, LP [Member]              
Business Acquisition [Line Items]              
Noncontrolling interest distributed   50.00%          
Eastern Energy Gas Holdings, LLC [Member] | Dominion Energy Questar Pipeline [Member] | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations [Member]              
Business Acquisition [Line Items]              
Distribution of net assets         699    
Stockholders' Equity, Distribution Of Net Assets Of Subsidiary To Affiliate, Cash         41    
Contributions         1,300    
Eastern Energy Gas Holdings, LLC [Member] | Dominion Energy Questar Pipeline [Member] | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations [Member] | Goodwill [Member]              
Business Acquisition [Line Items]              
Distribution of net assets         185    
Eastern Energy Gas Holdings, LLC [Member] | Dominion Energy Questar Pipeline [Member] | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations [Member] | Pension Plan Asset [Member]              
Business Acquisition [Line Items]              
Distribution of net assets         895    
Eastern Energy Gas Holdings, LLC [Member] | Dominion Energy Questar Pipeline [Member] | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations [Member] | Affiliated Balances              
Business Acquisition [Line Items]              
Distribution of net assets         107    
Eastern Energy Gas Holdings, LLC [Member] | Cove Point LNG, LP [Member]              
Business Acquisition [Line Items]              
Noncontrolling Interest, Increase from Sale of Parent Equity Interest         0    
Eastern Energy Gas Holdings, LLC [Member] | Cove Point LNG, LP [Member] | Noncontrolling Interest [Member]              
Business Acquisition [Line Items]              
Noncontrolling Interest, Increase from Sale of Parent Equity Interest         $ 2,765    
Eastern Energy Gas Holdings, LLC [Member] | Cove Point LNG, LP [Member] | GT&S Transaction [Member] | Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations [Member]              
Business Acquisition [Line Items]              
Noncontrolling interest distributed   50.00%          
Eastern Energy Gas Holdings, LLC [Member] | White River Hub, LLC [Member]              
Business Acquisition [Line Items]              
Equity method investment, ownership percentage         50.00%    
Eastern Energy Gas Holdings, LLC [Member] | Iroquois Gas Transmission System L.P. [Member]              
Business Acquisition [Line Items]              
Equity method investment, ownership percentage         50.00%    
Dominion Energy, Inc. [Member] | Cove Point LNG, LP [Member]              
Business Acquisition [Line Items]              
Retained interest after disposal   50.00%          
Ownership interest 25.00% 50.00%     50.00%