Debt (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Notes payable - current:
Uncommitted lines of credit	$ 54,082	$ 33,916
Other	565	296
Short-term Debt	54,647	34,212
Long-term debt:
Credit facility	382,000	300,000
Senior notes	225,000	300,000
Industrial development revenue bonds	11,900	11,900
Other	5,146	5,634
Long-term debt	$ 624,046	$ 617,534