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Subsequent Events (Details) - USD ($)
12 Months Ended
Jan. 31, 2018
Dec. 31, 2017
Jan. 30, 2018
Dec. 31, 2016
Black Diamond Gathering LLC        
Subsequent Event [Line Items]        
Investment acquired   54.40%    
Black Diamond Gathering LLC        
Subsequent Event [Line Items]        
Payment to Expand Acreage Dedication   $ 24,100,000    
Increase in Duration of the Acreage Dedication   5 years    
Saddle Butte | Subsequent Event        
Subsequent Event [Line Items]        
Payments to acquire businesses $ 319,900,000      
Saddle Butte | Black Diamond Gathering LLC | Subsequent Event        
Subsequent Event [Line Items]        
Payments to acquire businesses 638,500,000      
Greenfield Member | Black Diamond Gathering LLC        
Subsequent Event [Line Items]        
Investment acquired   45.60%    
Greenfield Member | Saddle Butte | Subsequent Event        
Subsequent Event [Line Items]        
Payments to acquire businesses 318,600,000      
Revolving Credit Facility        
Subsequent Event [Line Items]        
Maximum borrowing capacity   $ 350,000,000    
Debt outstanding   $ 85,000,000   $ 0
Revolving Credit Facility | Subsequent Event        
Subsequent Event [Line Items]        
Maximum borrowing capacity 530,000,000   $ 350,000,000  
Debt outstanding 410,000,000      
Revolving Credit Facility | Saddle Butte | Subsequent Event        
Subsequent Event [Line Items]        
Proceeds from borrowings $ 300,000,000