Changes in Accrued Warranty Balances (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2013		Aug. 31, 2012
Product Liability Contingency [Line Items]
Beginning Balance	$ 9,330		$ 14,751
Deductions	(4,796)	[1]	(3,905)	[1]
Provision charged to SG&A expense	5,308		3,681
Ending Balance	$ 9,842		$ 14,527

[1] Primarily claims paid during the year.