Property, Plant and Equipment, Net (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Property, Plant and Equipment
Property, plant and equipment, gross	$ 412,521	$ 394,705	$ 364,127
Accumulated depreciation and amortization	(206,971)	(201,540)	(194,869)
Property, plant and equipment excluding capital projects in progress, net	205,550	193,165	169,258
Capital projects in progress	3,910	2,551	15,348
Property, plant and equipment, net	209,460	195,716	184,606
Land
Property, Plant and Equipment
Property, plant and equipment, gross	32,601	28,996	29,287
Buildings and site improvements
Property, Plant and Equipment
Property, plant and equipment, gross	165,085	153,597	143,227
Leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, gross	3,793	3,820	3,794
Machinery and equipment
Property, Plant and Equipment
Property, plant and equipment, gross	$ 211,042	$ 208,292	$ 187,819

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

+ References+ Details

Gross amount, at the balance sheet date, of long-lived physical assets used in the normal conduct of business and not intended for resale. This can include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References+ Details

- Definition

Tangible assets that are held by an entity for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References+ Details