Accrued Liabilities (Accrued Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accrued Liabilities [Abstract]
Lease operating expenses	$ 17,220	$ 20,709
Employee costs	12,641	31,451
Interest payable	6,321	6,654
Taxes	3,767	3,284
Third-party credits	3,326	2,825
Other	3,643	5,248
Total accrued liabilities	$ 46,918	$ 70,171