Other Accrued Liabilities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Current:
Employee benefits	$ 18,655	$ 16,549
Self insurance	7,023	6,686
Environmental	194	240
Other	5,647	5,886
Total	31,519	29,361
Noncurrent:
Workers compensation payments	1,349	1,243
Environmental	140	165
Other	482	483
Total	$ 1,971	$ 1,891