Quarterly report pursuant to Section 13 or 15(d)

Debt (Details)

v3.10.0.1
Debt (Details)
$ in Thousands
9 Months Ended 12 Months Ended
Sep. 30, 2018
USD ($)
Dec. 31, 2017
USD ($)
Oct. 24, 2018
USD ($)
Debt      
Repayment of credit facility $ 100,000    
Reserve-Based Revolving Credit Facility      
Debt      
Maximum borrowing capacity 170,000 $ 170,000 $ 170,000
Repayment of credit facility 100,000    
Repayment from available cash 50,000    
Repayment of debt 50,000    
Amount drawn from credit facility 28,100 128,100  
Availability under the facility $ 140,000    
Weighted-average interest rate (as a percent) 6.70%    
Unamortized debt issuance costs $ 900 1,200  
Commitment fee (as a percent) 0.50    
Letter of Credit      
Debt      
Outstanding letters of credit amount $ 1,900 $ 1,900  
LIBOR Loans | Reserve-Based Revolving Credit Facility      
Debt      
Interest rate added to base rate (as a percent) 4.50%    
LIBOR floor rate 1.00%    
Minimum      
Debt      
EBITDA to interest expense coverage ratio 2.50    
Maximum      
Debt      
Total net indebtedness to EBITDA 4.00