Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Accrued Liabilities, Current [Abstract]
Accrued salaries, wages and benefits	$ 3,311	$ 3,552
Accrual for self-insurance liabilities	3,442	3,806
Property taxes	924	2,458
Other accrued expenses	2,742	2,640
Total accrued liabilities	$ 10,419	$ 12,456