Changes in Accrued Warranty Balances (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Feb. 28, 2015		Feb. 28, 2014		Feb. 28, 2015		Feb. 28, 2014
Product Liability Contingency [Line Items]
Beginning Balance	$ 8,958		$ 8,579		$ 14,741		$ 9,330
Acquisition of SPHC and subsidiaries	2,978				2,978
Deductions	(4,128)	[1]	(4,584)	[1]	(23,869)	[1]	(16,559)	[1]
Provision charged to SG&A expense	3,907		3,761		17,865		14,985
Ending Balance	$ 11,715		$ 7,756		$ 11,715		$ 7,756

[1] Primarily claims paid during the year.