Property, Plant and Equipment - Summary of Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Nov. 30, 2015	May. 31, 2015
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 254,426	$ 219,050
Accumulated depreciation and amortization	(131,205)	(121,124)
Property, plant and equipment, net	123,221	97,926
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	3,136	3,025
Buildings and leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	29,627	27,390
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	173,600	154,891
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	6,576	5,939
Capitalized ERP system development costs [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	23,885	14,524
Computers and computer software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	7,966	7,252
Automobiles [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	5,384	3,095
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 4,252	$ 2,934