Summary of Property, Plant and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Nov. 30, 2013	May 31, 2013
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 193,177	$ 179,990
Accumulated depreciation and amortization	(113,449)	(105,051)
Property, plant, and equipment, net	79,728	74,939
Land
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,087	3,108
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	19,215	18,445
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	145,431	137,439
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	4,790	4,469
Capitalized ERP System Development Costs
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	850
Computers and computer software
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	9,387	8,871
Automobiles
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,517	3,842
Construction in progress
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 6,900	$ 3,816