Segment Reporting and Related Disclosures - Marginal Contribution by Segment (Details) - USD ($) $ in Thousands	3 Months Ended
Aug. 31, 2015	Aug. 31, 2014
Segment Reporting Information [Line Items]
Marginal contribution	$ 12,640	$ 15,397
Unallocated SG&A expenses	8,447	7,938
Interest income/(expense), net	(242)	103
Income before income taxes	3,951	7,562
Operating Segments \| T&M
Segment Reporting Information [Line Items]
Marginal contribution	11,707	14,716
Operating Segments \| DP
Segment Reporting Information [Line Items]
Marginal contribution	$ 933	$ 681

Operating Income Excluding Fixed Selling, General and Administrative Expense

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Selling, General and Administrative Expense, Fixed Costs

+ References

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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

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))

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- Definition

The net amount of operating interest income (expense).

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.10)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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-Name Regulation S-X (SX)

-Number 210

-Section 04

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-Article 9

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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