Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Accrued Liabilities, Current [Abstract]
Accrued salaries, wages and benefits	$ 3,617	$ 3,552
Accrual for self-insurance liabilities	3,662	3,806
Property taxes	2,101	2,458
Other accrued expenses	1,580	2,640
Total accrued liabilities	$ 10,960	$ 12,456