Summary of Property, Plant and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2015	May 31, 2014
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 210,488	$ 203,621
Accumulated depreciation and amortization	(117,364)	(113,660)
Property, plant and equipment, net	93,124	89,961
Land
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,024	3,078
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	27,081	26,793
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	149,901	150,050
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	5,558	5,530
Capitalized ERP system development costs
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	11,772	4,655
Computers and computer software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	6,895	6,842
Automobiles
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,361	3,550
Construction in progress
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2,896	$ 3,123