Changes in Carrying Amount of Goodwill and Other Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill, Beginning Balance			$ 3,109
Goodwill, Additions
Goodwill, Ending Balance	3,109		3,109
Goodwill and other intangible assets, Beginning balance			4,310
Goodwill and other intangible assets, Additions
Amortization	(41)	(42)	(123)	(112)
Goodwill and other intangible assets, Ending balance	4,187		4,187
Customer relationships, Ending Balance	667		667
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Trade name, Beginning balance			411
Trade name, Additions
Trade name, Ending balance	411		411
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Customer relationships, Beginning Balance			790
Customer relationships, Additions
Amortization			(123)
Customer relationships, Ending Balance	$ 667		$ 667