Inventories - Schedule of Inventories (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2014	May 31, 2013
Inventory Disclosure [Abstract]
Raw materials	$ 23,319	$ 18,362
Work in process	13,353	11,006
Finished goods	23,162	25,694
Inventories	$ 59,834	$ 55,062

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Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer.

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

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Amount before valuation and LIFO reserves of merchandise or goods in the production process expected to be completed within one year or operating cycle, if longer.

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