Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accrued Liabilities, Current [Abstract]
Accrued salaries, wages and benefits	$ 3,552	$ 2,913
Accrual for self-insurance liabilities	3,806	3,401
Property taxes	2,458	2,358
Other accrued expenses	2,640	667
Total accrued liabilities	$ 12,456	$ 9,339