Changes in Accrued Warranty Balances (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2012		Aug. 31, 2011
Product Liability Contingency [Line Items]
Beginning Balance	$ 14,751		$ 17,196
Deductions	(3,905)	[1]	(4,072)	[1]
Provision charged to SG&A expense	3,681		3,841
Ending Balance	$ 14,527		$ 16,965

[1] Primarily claims paid during the year.