Summary of Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2014
Goodwill [Line Items]
Balance at beginning of year	$ 113,763
Acquisitions
Foreign currency adjustments	(622)
Balance at end of year	113,141
MS Segment
Goodwill [Line Items]
Balance at beginning of year	19,685
Acquisitions
Foreign currency adjustments	(427)
Balance at end of year	19,258
IHT Segment
Goodwill [Line Items]
Balance at beginning of year	63,249
Acquisitions
Foreign currency adjustments	(78)
Balance at end of year	63,171
Quest Integrity Group
Goodwill [Line Items]
Balance at beginning of year	30,829
Acquisitions
Foreign currency adjustments	(117)
Balance at end of year	$ 30,712