Segment Data for our Three Operating Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2014	Aug. 31, 2013
Segment Reporting Information [Line Items]
Revenues	$ 188,121	$ 174,311
Operating income	11,825	8,105
Capital expenditures	5,468	6,223
Depreciation and amortization	5,529	5,383
Operating Segments | IHT Segment
Segment Reporting Information [Line Items]
Revenues	105,594	95,833
Operating income	12,287	10,227
Capital expenditures	1,539	1,845
Depreciation and amortization	2,001	2,082
Operating Segments | MS Segment
Segment Reporting Information [Line Items]
Revenues	67,846	65,769
Operating income	6,704	6,833
Capital expenditures	1,180	1,647
Depreciation and amortization	1,864	1,778
Operating Segments | Quest Integrity Group
Segment Reporting Information [Line Items]
Revenues	14,681	12,709
Operating income	767	(685)
Capital expenditures	796	1,956
Depreciation and amortization	1,405	1,325
Corporate and shared support services
Segment Reporting Information [Line Items]
Operating income	(7,933)	(8,270)
Capital expenditures	1,953	775
Depreciation and amortization	$ 259	$ 198