Quarterly report pursuant to Section 13 or 15(d)

Debt (Detail)

v3.3.0.814
Debt (Detail)
$ in Millions
3 Months Ended 6 Months Ended 9 Months Ended
Sep. 30, 2015
USD ($)
Sep. 30, 2014
USD ($)
Jun. 30, 2015
Sep. 30, 2015
USD ($)
Sep. 30, 2014
USD ($)
Apr. 30, 2015
Jan. 31, 2014
USD ($)
Line Of Credit Facility [Line Items]              
Borrowings under credit facility $ 15.0     $ 15.0      
Debt maturity period       2019-12      
Ratio of net debt to EBITDAX     3.0        
Incurred interest expense 0.4     $ 1.1      
Capitalized interest expense $ 0.2 $ 0.3   $ 0.8 $ 0.8    
Maximum [Member]              
Line Of Credit Facility [Line Items]              
Ratio of net debt to EBITDAX       3.0      
Ratio of indebtedness to net capital           1.5  
Revolving Credit Facility [Member]              
Line Of Credit Facility [Line Items]              
Maximum borrowing capacity under loan agreement             $ 65.0