Accrued Liabilities (Accrued Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Accrued Liabilities [Abstract]
Employee costs	$ 15,394	$ 12,641
Lease operating expenses	10,075	17,220
Interest payable	6,524	6,321
Third-party credits	2,998	3,326
Taxes	2,219	3,767
Other	2,441	3,643
Total accrued liabilities	$ 39,651	$ 46,918