Changes in Accrued Warranty Balances (Detail) - USD ($) $ in Thousands		3 Months Ended
		Aug. 31, 2015	Aug. 31, 2014
Product Liability Contingency [Line Items]
Beginning Balance		$ 11,663	$ 14,741
Deductions	[1]	(4,660)	(14,675)
Provision charged to SG&A expense		3,109	7,355
Ending Balance		$ 10,112	$ 7,421

[1] Primarily claims paid during the year.