Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Components of property, plant and equipment
Land	$ 19,699	$ 17,655	$ 15,402
Land improvements and leasehold improvements	59,375	47,958	45,753
Buildings and storage facilities	178,354	150,461	144,834
Machinery and equipment	257,926	191,833	188,552
Software	12,632	10,861	10,873
Construction in progress	28,582	13,006	17,323
Property, plant and equipment, gross	556,568	431,774	422,737
Less accumulated depreciation and amortization	273,174	256,687	257,844
Property, plant and equipment, net	$ 283,394	$ 175,087	$ 164,893