INVENTORIES (Details) - USD ($) $ in Thousands	Sep. 26, 2021	Dec. 27, 2020
Inventory Disclosure [Abstract]
Raw materials and work-in-process	$ 1,040,242	$ 868,369
Finished products	382,799	356,052
Operating supplies	62,830	66,495
Maintenance materials and parts	70,950	67,877
Total inventories	$ 1,556,821	$ 1,358,793

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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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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date for elements of machinery or equipment held for the purpose of replacing similar parts in the course of repair or maintenance.

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of products used directly or indirectly in the manufacturing or production process, which may or may not become part of the final product. May also include items used in the storage, presentation or transportation of physical goods.

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The aggregate carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of items which are partially completed at the time of measurement and unprocessed items that will go through the production process and become part of the final product. This element may be used when the reporting entity combines work in process and raw materials into an aggregate amount.

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