Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies (Narrative) (Details)

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Commitments and Contingencies (Narrative) (Details)
$ in Thousands
 3 Months Ended 6 Months Ended 9 Months Ended 12 Months Ended
Jul. 29, 2016
defendant
Feb. 09, 2016
defendant
Mar. 11, 1997
Sep. 30, 2016
USD ($)
Jul. 29, 2016
complaint
Sep. 30, 2017
USD ($)
well
Sep. 30, 2016
USD ($)
Dec. 31, 1997
USD ($)
well
Commitments [Line Items]                
Plugging and abandonment trust on the WCBB properties           $ 3,100    
Number of claims filed | complaint         2      
Judicial District Court for the Parish of Cameron                
Commitments [Line Items]                
Number of defendants | defendant   26            
Judicial District Court for the Parish of Vermillion                
Commitments [Line Items]                
Number of defendants | defendant 40              
Loss on long-term purchase commitment | Muskie Proppant LLC                
Commitments [Line Items]                
Non-utilization fees, accrued damages year to date       $ 200   $ 0 $ 2,100  
Minimum                
Commitments [Line Items]                
Operating lease, term (in years)           1 year    
WCBB                
Commitments [Line Items]                
Remaining interest in oil and gas property acquisition, percent               50.00%
Payments of seller's obligation to contribute               $ 18
Minimum number of wells to be plugged | well               20
Tenure of minimum wells to be plugged (in years)     20 years          
Number of wells plugged | well           551    
Transportation commitment                
Commitments [Line Items]                
Firm transportation contracted with third parties           $ 3,726,745