Accrued Liabilities (Accrued Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accrued Liabilities, Current [Abstract]
Interest payable	$ 17,480	$ 6,524
Employee costs	14,526	15,394
Lease operating expenses	12,686	10,075
Taxes	9,982	2,219
Third-party credits	2,184	2,998
Other	3,274	2,441
Total accrued liabilities	$ 60,132	$ 39,651