Changes in Carrying Amount of Goodwill and Other Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2013	May 31, 2012	May 31, 2011
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, Beginning Balance	$ 3,109	$ 3,109
Goodwill, Additions
Goodwill, Ending Balance	3,109	3,109	3,109
Goodwill and other intangible assets, Beginning balance	4,310	4,323
Goodwill and other intangible assets, Additions		140
Amortization	(164)	(153)	(184)
Goodwill and other intangible assets, Ending balance	4,146	4,310	4,323
Customer relationships, Ending Balance	626
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Trade name, Beginning balance	411	411
Trade name, Additions
Trade name, Ending balance	411	411
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Customer relationships, Beginning Balance	790	803
Customer relationships, Additions		140
Amortization	(164)	(153)
Customer relationships, Ending Balance	$ 626	$ 790