Changes in Accrued Warranty Balances (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Commitments And Contingencies Disclosure [Abstract]
Beginning Balance		$ 14,457	$ 15,954	$ 19,149	$ 13,314
Deductions	[1]	(5,776)	(3,662)	(20,447)	(12,094)
Provision charged to expense		2,540	7,308	12,519	18,380
Ending Balance		$ 11,221	$ 19,600	$ 11,221	$ 19,600

[1] Primarily claims paid during the year.