Accrued Liabilities (Accrued Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accrued Liabilities [Abstract]
Employee costs	$ 19,373	$ 22,056
Interest payable	17,483	6,635
Lease operating expenses	10,069	12,756
Taxes	9,811	1,378
Customer prepayments	8,683	0
Third-party credits	2,611	2,129
Other	5,244	4,710
Total accrued liabilities	$ 73,274	$ 49,664