Changes in Accrued Warranty Balances (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Nov. 30, 2012		Nov. 30, 2011		Nov. 30, 2012		Nov. 30, 2011
Product Liability Contingency [Line Items]
Beginning Balance	$ 14,527		$ 16,965		$ 14,751		$ 17,196
Deductions	(4,082)	[1]	(4,833)	[1]	(7,987)	[1]	(8,905)	[1]
Provision charged to SG&A expense	4,693		4,198		8,374		8,039
Ending Balance	$ 15,138		$ 16,330		$ 15,138		$ 16,330

[1] Primarily claims paid during the year.