Quarterly report pursuant to Section 13 or 15(d)

Revenue (Revenues from Contracts with Customers) (Details)

v3.19.2
Revenue (Revenues from Contracts with Customers) (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Disaggregation of Revenue [Line Items]        
Carried interest recoupment $ 733 $ 705 $ 1,440 $ 1,356
Royalties (3,799) (3,472) (6,552) (7,134)
Total revenue, net 25,230 24,426 44,995 52,071
Sales Under COSPA [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from customer contracts 20,949 $ 27,193 42,760 55,656
Gabonese Government Share Of Profit Oil [Member]        
Disaggregation of Revenue [Line Items]        
Revenue from customer contracts       $ 2,193
Revenue not from customer contracts $ 7,347   $ 7,347