Changes in Accrued Warranty Balances (Detail) - USD ($) $ in Thousands		3 Months Ended
		Aug. 31, 2020	Aug. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Beginning Balance		$ 11,106	$ 10,414
Deductions	[1]	(5,930)	(5,513)
Provision charged to expense		7,660	5,168
Ending Balance		$ 12,836	$ 10,069

[1] Primarily claims paid during the year.