Components of Income Before Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
May. 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May. 31, 2014	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	May. 31, 2015	May. 31, 2014	May. 31, 2013
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Domestic									$ 24,203	$ 30,907	$ 37,162
Foreign									447	1,619	(49)
Income before income taxes	$ 5,646	$ 3,746	$ 7,696	$ 7,562	$ 7,368	$ 7,291	$ 8,999	$ 8,868	$ 24,650	$ 32,526	$ 37,113

Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]

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- Definition

The portion of earnings or loss from continuing operations before income taxes that is attributable to domestic operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(1)(i))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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- Definition

The portion of earnings or loss from continuing operations before income taxes that is attributable to foreign operations, which is defined as Income or Loss generated from operations located outside the entity's country of domicile.

+ References

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- Definition

Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest.

+ References

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