Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Property, plant and equipment
Property, plant and equipment, Gross	$ 256,487	$ 249,778
Accumulated depreciation	(195,795)	(188,894)
Total property, plant and equipment, net	60,692	60,884
Manufacturing equipment [Member]
Property, plant and equipment
Property, plant and equipment, Gross	174,353	170,304
Land [Member]
Property, plant and equipment
Property, plant and equipment, Gross	8,101	8,101
Buildings and improvements [Member]
Property, plant and equipment
Property, plant and equipment, Gross	53,792	53,539
Office furniture and research equipment [Member]
Property, plant and equipment
Property, plant and equipment, Gross	$ 20,241	$ 17,834

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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Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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