Summary of Other Assets (Detail) - USD ($) $ in Thousands	May. 31, 2015	May. 31, 2014
Other Assets [Line Items]
Net investment in sales-type leases	$ 5,876	$ 7,264
Supplemental executive retirement plan assets	3,521	3,418
Demonstration equipment	81	6,659
Income taxes receivable	0	1,831
Prepaid and other assets	4,265	2,978
Total other assets	$ 13,743	$ 22,150