Quarterly report pursuant to Section 13 or 15(d)

Acquisitions And Dispositions (Narrative) (Details)

v3.5.0.2
Acquisitions And Dispositions (Narrative) (Details)
a in Millions
 1 Months Ended 9 Months Ended
Sep. 21, 2016
USD ($)
item
Jul. 28, 2016
Mar. 14, 2016
USD ($)
Jan. 01, 2014
Nov. 30, 2006
a
item
Sep. 30, 2016
USD ($)
item
Oct. 17, 2016
USD ($)
Dec. 31, 2015
USD ($)
Apr. 30, 2014
USD ($)
Business Acquisition [Line Items]                  
Fair value of fields           $ 410,301,000   $ 412,593,000  
Fair value of fields           10,000,000   10,000,000  
Restricted cash           830,000   $ 15,830,000  
Additional Term Loan Available Until Dec. 31, 2016 [Member]                  
Business Acquisition [Line Items]                  
Notes Payable to Bank           $ 5,000,000      
Hefley Field [Member]                  
Business Acquisition [Line Items]                  
Number of wells, interest for sale | item 2                
Fair value of fields $ 850,000                
East Poplar Dome Field [Member] | Subsequent Event [Member]                  
Business Acquisition [Line Items]                  
Fair value of fields             $ 250,000    
Joint Operating With Republic Of Angola [Member]                  
Business Acquisition [Line Items]                  
Production license agreement term           4 years      
Production license agreement term extended by government           3 years      
Area under acquire property exploration rights agreement term (acres) | a         1.4        
Number of exploration wells | item         2        
Number Of Additional Exploration Wells | item         2        
Joint operation agreement related to third party in working interest percentage         40.00%        
Additional joint operation agreement related to third party in working interest percentage         10.00%        
Drilling commitment, net           $ 5,000,000      
Restricted cash           15,000,000      
Liability for the penalty           $ 15,000,000      
Working interest ownership other, percentage       40.00%          
Allowance for accounts with partners                 $ 7,600,000
Joint Operating With Republic Of Angola [Member] | Drilling or Commencing Wells By November 30, 2017 [Member]                  
Business Acquisition [Line Items]                  
Number of exploration wells | item           4      
Joint Operating With Republic Of Angola [Member] | Remaining Obligation [Member]                  
Business Acquisition [Line Items]                  
Number of exploration wells | item           3      
Etame [Member]                  
Business Acquisition [Line Items]                  
Percentage of working interest   2.98%              
Percentage of participating interest   3.23%              
Etame [Member] | Additional Term Loan Available Until Dec. 31, 2016 [Member]                  
Business Acquisition [Line Items]                  
Notes Payable to Bank           $ 5,000,000      
Sonangol P&P [Member]                  
Business Acquisition [Line Items]                  
Payment from joint venture partners     $ 19,000,000            
Reversal of allowance     7,600,000            
Interest income     $ 3,200,000