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Goodwill and Other Intangible Assets (Details) - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Jan. 03, 2018
Dec. 31, 2017
Dec. 14, 2017
Dec. 13, 2017
Goodwill [Line Items]            
Goodwill $ 796,359,000     $ 0    
Amortization expense $ 1,922,000 $ 0        
Useful life, customer relationship intangible assets 17 years          
Midstream Acquisition [Member]            
Goodwill [Line Items]            
Goodwill     $ 796,359,000      
Other intangible assets     $ 128,781,000      
CNX Gathering LLC [Member]            
Goodwill [Line Items]            
Ownership percentage in equity method investment 50.00%   50.00%   50.00% 50.00%