Segment Data for our Three Operating Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014
Segment Reporting Information [Line Items]
Revenues	$ 174,589us-gaap_SalesRevenueNet	$ 163,236us-gaap_SalesRevenueNet	$ 603,329us-gaap_SalesRevenueNet	$ 538,040us-gaap_SalesRevenueNet
Operating income	2,926us-gaap_OperatingIncomeLoss	1,000us-gaap_OperatingIncomeLoss	43,425us-gaap_OperatingIncomeLoss	32,986us-gaap_OperatingIncomeLoss
Capital expenditures	7,287	10,139	18,712	23,758
Depreciation and amortization	5,688	5,285	16,852	15,976
Operating Segments \| IHT Segment
Segment Reporting Information [Line Items]
Revenues	95,350	85,149	335,024	290,409
Operating income	7,536	3,783	41,822	31,666
Capital expenditures	2,029	2,187	5,893	5,602
Depreciation and amortization	2,138	1,936	6,207	5,947
Operating Segments \| MS Segment
Segment Reporting Information [Line Items]
Revenues	64,999	63,440	217,066	200,196
Operating income	3,357	2,939	18,870	17,120
Capital expenditures	797	1,503	2,884	4,694
Depreciation and amortization	1,850	1,801	5,598	5,391
Operating Segments \| Quest Integrity
Segment Reporting Information [Line Items]
Revenues	14,240	14,647	51,239	47,435
Operating income	100	1,170	7,217	5,986
Capital expenditures	855	582	2,466	3,257
Depreciation and amortization	1,429	1,343	4,254	4,033
Corporate and shared support services
Segment Reporting Information [Line Items]
Operating income	(8,067)	(6,892)	(24,484)	(21,786)
Capital expenditures	3,606	5,867	7,469	10,205
Depreciation and amortization	$ 271	$ 205	$ 793	$ 605

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

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- Definition

The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585

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- Definition

Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

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