Quarterly report pursuant to Section 13 or 15(d)

Oil And Natural Gas Properties And Equipment (Narrative) (Detail)

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Oil And Natural Gas Properties And Equipment (Narrative) (Detail)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2016
USD ($)
item
Jun. 30, 2016
USD ($)
Sep. 30, 2015
USD ($)
Sep. 30, 2016
USD ($)
Sep. 30, 2015
USD ($)
Dec. 31, 2015
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Fair value of fields $ 410,301     $ 410,301   $ 412,593
Impairment of proved properties $ 88   $ 17,988 88 $ 29,208  
Etame Field [Member]            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Impairment of proved properties   $ 0        
North Texas [Member]            
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]            
Number of wells, interest for sale | item 2          
Fair value of fields $ 850     $ 850    
Impairment of proved properties $ 100