v2.4.0.6
Revolving Credit Facility - Additional Information (Detail) (USD $)
3 Months Ended
Mar. 31, 2013
Ratio
Dec. 31, 2012
Line of Credit Facility [Line Items]    
Maximum borrowing revolving credit facility $ 300,000,000  
Revolving credit facility, borrowing base 280,000,000  
Maturity period of revolving credit facility Jul. 31, 2014  
Revolving credit facility, interest rate description Borrowings bear interest based on the agent bank's prime rate plus an applicable margin ranging from 0.75% to 1.75%, or the sum of the Eurodollar rate plus an applicable margin ranging from 1.75% to 2.75%  
Annual commitment fee of unused borrowings 0.50%  
Amount outstanding under revolving credit facility 152,300,000 106,000,000
Interest rate applicable of revolving credit facility 2.70% 2.70%
Unused letters of credit outstanding 325,000  
Consolidated current assets ratio 1.0  
Consolidated current liabilities ratio 1.0  
Consolidated funded debt ratio 4.0  
Consolidated earnings before interest taxes depreciation amortization and exploration expenses ratio 1.0  
Debt default description In addition, our credit agreement contains customary events of default that would permit our lenders to accelerate the debt under our credit agreement if not cured within applicable grace periods, including, among others, failure to make payments of principal or interest when due, materially incorrect representations and warranties, failure to make mandatory prepayments in the event of borrowing base deficiencies, breach of covenants, defaults upon other obligations in excess of $500,000, events of bankruptcy, the occurrence of one or more unstayed judgments in excess of $500,000 not covered by an acceptable policy of insurance, failure to pay any obligation in excess of $500,000 owed under any derivatives transaction or in any amount if the obligation under the derivatives transaction is secured by collateral under the credit agreement, any event of default by the Company occurs under any agreement entered into in connection with a derivatives transaction, liens securing the loans under the credit agreement cease to be in place, a Change in Control (as defined in the credit agreement) of the Company occurs, and dissolution of the Company.  
Debt default amount 500,000  
Covenants agreements one [Member]
   
Line of Credit Facility [Line Items]    
Covenant description A consolidated modified current ratio covenant that requires us to maintain a ratio of not less than 1.0 to 1.0 at all times  
Covenants agreements two [Member]
   
Line of Credit Facility [Line Items]    
Ratio covenant description A consolidated funded debt to consolidated EBITDAX ratio covenant that requires us to maintain a ratio of not more than 4.0 to 1.0 at the end of each fiscal quarter  
Minimum [Member]
   
Line of Credit Facility [Line Items]    
Increase in the borrowing base for line of credit facility 280,000,000  
Increased lender's aggregate maximum commitment 300,000,000  
Minimum [Member] | Interest rate calculation one [Member]
   
Line of Credit Facility [Line Items]    
Revolving credit facility, marginal percentage 0.75%  
Minimum [Member] | Interest rate calculation two [Member]
   
Line of Credit Facility [Line Items]    
Revolving credit facility, marginal percentage 1.75%  
Maximum [Member]
   
Line of Credit Facility [Line Items]    
Maturity period of revolving credit facility Jul. 31, 2016  
Increase in the borrowing base for line of credit facility 315,000,000  
Increased lender's aggregate maximum commitment $ 500,000,000  
Maximum [Member] | Interest rate calculation one [Member]
   
Line of Credit Facility [Line Items]    
Revolving credit facility, marginal percentage 1.75%  
Maximum [Member] | Interest rate calculation two [Member]
   
Line of Credit Facility [Line Items]    
Revolving credit facility, marginal percentage 2.75%