Changes in Accrued Warranty Balances (Detail) - USD ($) $ in Thousands		3 Months Ended
		Aug. 31, 2016	Aug. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Beginning Balance		$ 13,314	$ 11,663
Deductions	[1]	(2,490)	(4,660)
Provision charged to expense		4,409	3,109
Ending Balance		$ 15,233	$ 10,112

[1] Primarily claims paid during the year.