Note 6 - Property and Equipment, Net (Details) - Property and Equipment - USD ($) $ in Thousands	Aug. 31, 2015	May. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 135,526	$ 133,058
Less accumulated depreciation	(62,186)	(59,484)
Property and equipment, net	73,340	73,574
Land [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	238	250
Building and Building Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,357	2,494
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	25,816	25,639
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,100	6,897
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,765	3,757
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 95,250	$ 94,021