Debt (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Notes payable - current:
Uncommitted lines of credit	$ 39,281	$ 21,572
Other	144	150
Short-term Debt	39,425	21,722
Long-term debt:
Credit facility	303,000	291,000
Senior notes	300,000	300,000
Industrial development revenue bonds	11,900	11,900
Other	3,195	3,254
Long-term debt	$ 618,095	$ 606,154