Summary of Significant Accounting Policies and Practices - Schedule of Rollforward Goodwill (Detail) $ in Thousands	6 Months Ended
	Nov. 30, 2015 USD ($)
Goodwill [Line Items]
Balance at beginning of period	$ 107,773
Acquisitions	147,923
Foreign currency adjustments	(2,019)
Balance at end of period	253,677
IHT Segment [Member]
Goodwill [Line Items]
Balance at beginning of period	60,737
Acquisitions	145,440
Foreign currency adjustments	(1,152)
Balance at end of period	205,025
MS Segment [Member]
Goodwill [Line Items]
Balance at beginning of period	17,466
Acquisitions	2,483
Foreign currency adjustments	(363)
Balance at end of period	19,586
Quest Integrity [Member]
Goodwill [Line Items]
Balance at beginning of period	29,570
Foreign currency adjustments	(504)
Balance at end of period	$ 29,066