Working Capital (Schedule Of Inventories) (Details) (USD $) In Thousands, unless otherwise specified	Nov. 30, 2011	May 31, 2011
Total inventories	$ 128,154	$ 140,646
LIFO Cost [Member]
Finished products	8,384	9,627
Work in process	35,579	44,391
Raw materials	12,888	15,215
Total inventories at LIFO cost	56,851	69,233
Average Cost [member]
Finished products	22,445	23,427
Raw materials	114	272
Parts and supplies	48,744	47,714
Total inventories at average cost	$ 71,303	$ 71,413

Carrying amount as of the balance sheet date of merchandise or goods held by the company that are readily available for sale.

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Carrying amount (lower of cost or market) as of the balance sheet date of inventories less all valuation and other allowances. Excludes noncurrent inventory balances (expected to remain on hand past one year or one operating cycle, if longer).

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Carrying amount as of the balance sheet date of unprocessed items to be consumed in the manufacturing or production process. Also includes purchased parts that will be used as components of a finished product.

+ References

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Carrying amount as of the balance sheet date of merchandise or goods which are partially completed, are generally comprised of raw materials, labor and factory overhead costs, and 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 amount of LIFO (last in first out) inventory present at the reporting date when inventory is also valued using different valuation methods.

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Carrying amount 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 amount of weighted average cost inventory present at the reporting date when inventory is valued using different valuation methods.

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