Summary of Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2013	May 31, 2012
Goodwill [Line Items]
Balance at beginning of year	$ 95,002	$ 89,520
Acquisitions	7,788	8,926
Foreign currency adjustments	676	(3,444)
Balance at end of year	103,466	95,002
TCM Division
Goodwill [Line Items]
Balance at beginning of year	75,131	76,872
Acquisitions	9,009
Foreign currency adjustments	195	(1,741)
Balance at end of year	84,335	75,131
TMS Division
Goodwill [Line Items]
Balance at beginning of year	19,871	12,648
Acquisitions	(1,221)	8,926
Foreign currency adjustments	481	(1,703)
Balance at end of year	$ 19,131	$ 19,871