Changes in Accrued Warranty Balances (Detail) - USD ($) $ in Thousands		3 Months Ended
		Aug. 31, 2019	Aug. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Beginning Balance		$ 10,414	$ 11,721
Deductions	[1]	(5,513)	(6,614)
Provision charged to expense		5,168	5,478
Ending Balance		$ 10,069	$ 10,585

[1] Primarily claims paid during the year.