Annual report pursuant to Section 13 and 15(d)

Debt (Detail)

v3.3.1.900
Debt (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Jan. 31, 2014
Line Of Credit Facility [Line Items]      
Maximum borrowing capacity under loan agreement     $ 65,000
Credit facility borrowing base $ 20,100    
Borrowings under credit facility 15,000    
Long term debt 15,000 $ 15,000  
Incurred interest expense 1,500 1,200  
Capitalized interest expense $ 800 $ 1,200  
IFC Credit Facility [Member]      
Line Of Credit Facility [Line Items]      
Interest rate on outstanding borrowings 4.09% 4.32%  
Maximum [Member]      
Line Of Credit Facility [Line Items]      
Ratio of net debt to EBITDAX 3.0    
Senior Tranche [Member]      
Line Of Credit Facility [Line Items]      
Maximum borrowing capacity under loan agreement $ 50,000    
Decrease in debt instrument $ 6,250    
Debt instrument interest rate 3.75%    
Debt instrument, commitment fee 1.50%    
Subordinated Tranche [Member]      
Line Of Credit Facility [Line Items]      
Maximum borrowing capacity under loan agreement $ 15,000    
Decrease in debt instrument $ 1,880    
Debt instrument interest rate 5.75%    
Debt instrument, commitment fee 2.30%