Quarterly report pursuant to Section 13 or 15(d)

Segment Information (Segment Activity) (Details)

v3.10.0.1
Segment Information (Segment Activity) (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Segment Reporting Information [Line Items]        
Revenues-oil and natural gas sales $ 25,266 $ 18,178 $ 77,337 $ 59,869
Operating income (loss) 17,320 3,721 36,081 17,456
Other, net (1,029) (793) (2,184) (571)
Income tax expense (benefit) (62,224) 2,749 (54,600) 9,039
Additions to properties and equipment - accrual 17,986 297 18,955 1,111
Operating Segments [Member] | Gabon Segment [Member]        
Segment Reporting Information [Line Items]        
Revenues-oil and natural gas sales 25,265 18,162 77,333 59,823
Operating income (loss) 19,826 6,067 45,670 25,117
Other, net 3 142 (127) 441
Income tax expense (benefit) (42,141) 2,749 (34,517) 9,039
Additions to properties and equipment - accrual 17,983 237 18,938 1,051
Operating Segments [Member] | Equatorial Guinea Segment [Member]        
Segment Reporting Information [Line Items]        
Operating income (loss) (159) (44) (274) (97)
Other, net   4 (3) 13
Corporate And Other [Member]        
Segment Reporting Information [Line Items]        
Revenues-oil and natural gas sales 1 16 4 46
Operating income (loss) (2,347) (2,302) (9,315) (7,564)
Other, net (1,032) (939) (2,054) (1,025)
Income tax expense (benefit) (20,083)   (20,083)  
Additions to properties and equipment - accrual $ 3 $ 60 $ 17 $ 60