Changes in Accrued Warranty Balances (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Nov. 30, 2011		Nov. 30, 2010		Nov. 30, 2011		Nov. 30, 2010
Product Liability Contingency [Line Items]
Beginning Balance	$ 16,965		$ 15,940		$ 17,196		$ 17,602
Deductions	(4,833)	[1]	(5,471)	[1]	(8,905)	[1]	(11,283)	[1]
Provision charged to SG&A expense	4,198		5,462		8,039		9,612
Ending Balance	$ 16,330		$ 15,931		$ 16,330		$ 15,931

[1] Primarily claims paid during the period.