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Acquisitions, Investments and Dispositions - Mountain Valley Pipeline (Details) - CET Gas - Mountain Valley Pipeline - USD ($)
$ in Millions
1 Months Ended
Jan. 31, 2016
Dec. 31, 2019
Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]      
Percentage of equity interest acquired 12.50% 12.50%  
Payments to acquire equity interest $ 18    
Equity method investment   $ 530 $ 337
Expected reduction in equity interest   10.00%  
Minimum      
Schedule of Equity Method Investments [Line Items]      
Estimated project cost   $ 5,300  
Maximum      
Schedule of Equity Method Investments [Line Items]      
Equity method investment   530  
Estimated project cost   $ 5,500