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.

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The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

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- Definition

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.

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- 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.

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Property, Plant & Equipment (Details) (USD $)	3 Months Ended
Property, Plant & Equipment (Details) (USD $)	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 645,276,000		$ 614,263,000
Less accumulated depreciation	(274,105,000)		(267,833,000)
Total property, plant and equipment, net	371,171,000		346,430,000
Depreciation expense related to property, plant and equipment	7,200,000	5,100,000
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	27,898,000		28,021,000
Land improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	17,411,000		17,376,000
Buildings [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	227,735,000		212,428,000
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	324,490,000		310,352,000
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	9,128,000		9,144,000
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment	$ 38,614,000		$ 36,942,000