Changes in Carrying Amount of Goodwill and Other Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, Beginning Balance	$ 3,109	$ 3,109
Goodwill, Additions	0	0
Goodwill, Ending Balance	3,109	3,109	$ 3,109
Goodwill and other intangible assets, Beginning balance	3,982	4,146
Goodwill and other intangible assets, Additions	0	0
Amortization	(129)	(164)	(164)
Goodwill and other intangible assets, Ending balance	3,853	3,982	4,146
Customer relationships, Ending Balance	333
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Customer relationships, Beginning Balance	462	626
Customer relationships, Additions	0	0
Amortization	(129)	(164)
Customer relationships, Ending Balance	333	462	626
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Trade name, Beginning balance	411	411
Trade name, Additions	0	0
Trade name, Ending balance	$ 411	$ 411	$ 411