Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2013	May 31, 2012
ASSETS
Supplemental executive retirement plan	$ 2,932	$ 2,370
Fair Value, Measurements, Recurring
ASSETS
Total assets measured at fair value	4,017	5,056
Fair Value, Measurements, Recurring \| Money market funds
ASSETS
Money market funds	1,014	2,507
Fair Value, Measurements, Recurring \| Supplemental executive retirement plan
ASSETS
Supplemental executive retirement plan	2,932	2,370
Fair Value, Measurements, Recurring \| Foreign exchange forward contracts
ASSETS
Foreign exchange forward contracts	71	179
Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Fair Value, Measurements, Recurring
ASSETS
Total assets measured at fair value	3,946	4,877
Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Fair Value, Measurements, Recurring \| Money market funds
ASSETS
Money market funds	1,014	2,507
Quoted Prices in Active Markets for Identical Instruments (Level 1) \| Fair Value, Measurements, Recurring \| Supplemental executive retirement plan
ASSETS
Supplemental executive retirement plan	2,932	2,370
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring
ASSETS
Total assets measured at fair value	71	179
Significant Other Observable Inputs (Level 2) \| Fair Value, Measurements, Recurring \| Foreign exchange forward contracts
ASSETS
Foreign exchange forward contracts	$ 71	$ 179

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

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