Quarterly report pursuant to Section 13 or 15(d)

Impairment of Proved Properties (Detail)

v3.2.0.727
Impairment of Proved Properties (Detail)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2015
USD ($)
Mar. 31, 2015
USD ($)
Jun. 30, 2015
USD ($)
item
Jun. 30, 2014
USD ($)
Dec. 31, 2014
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Number of fields | item     5    
Fair value of fields $ 368,734   $ 368,734   $ 338,641
Impairment of proved properties 5,821   $ 11,220 $ 0  
Southeast Etame And North Tchibala field          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Number of drilled development wells | item     2    
Impairment of proved properties 5,800 $ 5,400      
Southeast Etame [Member] | Fair Value, Inputs, Level 3 [Member]          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Fair value of fields 9,100   $ 9,100    
North Tchibala [Member] | Fair Value, Inputs, Level 3 [Member]          
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]          
Fair value of fields $ 0   $ 0