Quarterly report pursuant to Section 13 or 15(d)

Debt (Detail)

v3.2.0.727
Debt (Detail)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2015
USD ($)
Jun. 30, 2014
USD ($)
Jun. 30, 2015
USD ($)
Jun. 30, 2014
USD ($)
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      
Average interest rate on bank debt     4.94%      
Incurred interest expense 0.4   $ 0.7      
Capitalized interest expense $ 0.3 $ 0.3 $ 0.5 $ 0.5    
Maximum            
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            
Line Of Credit Facility [Line Items]            
Maximum borrowing capacity under loan agreement           $ 65.0