Accrued Liabilities and Other (Schedule of Accrued Liabilities and Other Balances) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Liabilities and Other [Abstract]
Accrued accounts payable invoices	$ 3,947	$ 4,650
Joint venture audit settlement		3,322
Gabon DMO, PID and PIH obligations	4,762	3,314
Capital expenditures	1,325	11,792
Stock appreciation rights	823	2,638
Accrued wages and other compensation	1,797	1,731
Other	1,772	2,326
Total accrued liabilities and other	$ 14,426	$ 29,773