Inventories (Details) (USD $)	Mar. 29, 2015	Dec. 28, 2014
Inventory Disclosure [Abstract]
Raw materials	$ 20,859,000	$ 19,427,000
Work in process	30,910,000	30,797,000
Finished goods	23,264,000	24,453,000
Inventories	75,033,000us-gaap_InventoryNet	74,677,000us-gaap_InventoryNet
Inventory, noncurrent	7,000,000us-gaap_InventoryNoncurrent	6,400,000us-gaap_InventoryNoncurrent
Supplies inventory	$ 9,200,000us-gaap_MaterialsSuppliesAndOther	$ 8,800,000us-gaap_MaterialsSuppliesAndOther

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of merchandise or goods held by the company that are readily available for sale.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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Inventories not expected to be converted to cash, sold or exchanged within the normal operating cycle.

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Aggregated amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed. This amount is net of valuation reserves and adjustments.

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Carrying amount, net of reserves and adjustments, as of the balance sheet date of merchandise or goods which are partially completed. This inventory is generally comprised of raw materials, labor and factory overhead costs, which require further materials, labor and overhead to be converted into finished goods, and which generally require the use of estimates to determine percentage complete and pricing.

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The carrying amount of capitalized costs of materials, supplies, and other assets, which are not included in inventory but used in production.

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