Changes in Accrued Warranty Balances (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2014		Aug. 31, 2013
Product Liability Contingency [Line Items]
Beginning Balance	$ 14,741		$ 9,330
Deductions	(14,675)	[1]	(4,796)	[1]
Provision charged to SG&A expense	7,355		5,308
Ending Balance	$ 7,421		$ 9,842

[1] Primarily claims paid during the year.