Summary of Property, Plant and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Aug. 31, 2014	May 31, 2014
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 205,662	$ 203,621
Accumulated depreciation and amortization	(114,255)	(113,660)
Property, plant, and equipment, net	91,407	89,961
Land
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,076	3,078
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	27,101	26,793
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	149,632	150,050
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	5,530	5,530
Capitalized ERP system development costs
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	6,560	4,655
Computers and computer software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	6,758	6,842
Automobiles
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,406	3,550
Construction in progress
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 3,599	$ 3,123