Quarterly report pursuant to Section 13 or 15(d)

Contingencies - Additional Information (Details)

v2.4.0.8
Contingencies - Additional Information (Details) (USD $)
 1 Months Ended 3 Months Ended 9 Months Ended
Jan. 31, 2014
Sep. 30, 2014
Mar. 31, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Dec. 31, 2013
Dec. 31, 2010
Loss Contingencies [Line Items]                
Under payment of royalties $ 30,000              
Under payment percentage of total royalty payments 0.0045%              
Statutory fine payment relative to underpayment     2,300,000          
Insurance claims receivable   42,000,000     42,000,000      
Percentage of interest on reimbursement amount         18.00%      
Notified disallowed amount in reductions taken by ONRR               4,700,000
Settlement of lawsuits, fines, penalties and other   0   300,000 300,000 300,000    
Liability loss contingency   500,000     500,000   200,000  
Comprehensive General Liability policy
                
Loss Contingencies [Line Items]                
Insurance claims received         1,000,000      
Energy Package
                
Loss Contingencies [Line Items]                
Insurance claims received         1,000,000      
Liberty Mutual Insurance Co
                
Loss Contingencies [Line Items]                
Insurance claims received         5,000,000      
Revised estimate
                
Loss Contingencies [Line Items]                
Insurance claims receivable   $ 35,000,000     $ 35,000,000