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Variable Interest Entities - Narrative (Details)
12 Months Ended
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Oct. 31, 2015
mi
Mar. 31, 2014
Variable Interest Entity [Line Items]          
Proceeds from the sale of royalty trust units $ 0 $ 22,119,000 $ 28,985,000    
Pinon Gathering Company LLC          
Variable Interest Entity [Line Items]          
Number of miles of gathering lines acquired | mi       370  
Royalty Trusts          
Variable Interest Entity [Line Items]          
Percentage of royalty interest conveyed to company at trust termination 50.00%        
Percentage of royalty interest sold at trust termination 50.00%        
Percentage of subordinated units to total units 25.00%        
Percentage of cash available in excess of target distribution paid for incentive distribution 50.00%        
Conversion ratio of Royalty Trust subordinated unit to common units 1        
Outstanding balance under loan commitment $ 0 0      
Noncontrolling interest in VIEs 510,200,000 1,300,000,000      
Proceeds from the sale of royalty trust units   22,100,000 $ 29,000,000    
Total liabilities $ 1,060,000 $ 2,852,000      
Grey Ranch Plant, L.P          
Variable Interest Entity [Line Items]          
Beneficial interest owned by Company     50.00%    
Noncontrolling interest, ownership percentage by noncontrolling owners     50.00%    
Noncontrolling interest, decrease from redemptions percentage         50.00%
Grey Ranch Plant Genpar, LLC (Genpar)          
Variable Interest Entity [Line Items]          
Beneficial interest owned by Company     50.00%    
Noncontrolling interest, decrease from redemptions percentage         50.00%
Percentage ownership of another VIE     1.00%    
Total liabilities     $ 0