Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Liabilities, Current [Abstract]
Accrued salaries, wages and benefits	$ 9,632	$ 10,818
Accrual for insurance liabilities	5,233	5,223
Property taxes	513	1,615
Sales taxes	1,836	1,722
Interest	46	19
Other accrued expenses	613	549
Total accrued liabilities	$ 17,873	$ 19,946