Accrued Liabilities (Accrued Liabilities) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accrued Liabilities [Abstract]
Interest payable	$ 17,354	$ 6,635
Employee costs	10,356	22,056
Lease operating expenses	7,961	12,756
Taxes	4,059	1,378
Third-party credits	2,974	2,129
Other	5,380	4,710
Total accrued liabilities	$ 48,084	$ 49,664