Reconciliation of Denominator Used in Computation of Basic and Diluted Earnings per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2013	May 31, 2012	May 31, 2011
Denominator:
Denominator for basic earnings per share-weighted average common shares outstanding (including shares issuable for vested restricted stock units)									24,226	23,983	23,974
Effect of unvested restricted stock units									43	169	98
Diluted shares used in per share calculation									24,269	24,152	24,072
Net income	$ 6,392	$ 5,037	$ 6,239	$ 5,086	$ 6,253	$ 4,995	$ 6,019	$ 8,505	$ 22,754	$ 25,772	$ 23,756
Earnings per share:
Basic	$ 0.27	$ 0.21	$ 0.26	$ 0.21	$ 0.26	$ 0.21	$ 0.25	$ 0.35	$ 0.94	$ 1.07	$ 0.99
Diluted	$ 0.26	$ 0.21	$ 0.26	$ 0.21	$ 0.26	$ 0.21	$ 0.25	$ 0.35	$ 0.94	$ 1.07	$ 0.99

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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-Glossary Other Comprehensive Income

-URI http://asc.fasb.org/extlink&oid=6519514

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-Glossary Net Income

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-Name Accounting Research Bulletin (ARB)

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-Appendix A

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+ Details

- Definition

The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

+ References+ Details

- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References+ Details

- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

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-Glossary Weighted-Average Number of Common Shares Outstanding

-URI http://asc.fasb.org/extlink&oid=6528421

+ Details