Accrued Loss Reserves (Detail) - USD ($) $ in Thousands	May 31, 2020	May 31, 2019
Schedule Of Accrued Liabilities [Line Items]
Accrued losses	$ 20,021	$ 19,899
Accrued Loss Reserves - Noncurrent	34,654	37,554
Accrued product liability reserves
Schedule Of Accrued Liabilities [Line Items]
Accrued losses	10,458	11,739
Accrued Loss Reserves - Noncurrent	27,016	29,942
Accrued warranty reserves
Schedule Of Accrued Liabilities [Line Items]
Accrued losses	7,593	7,013
Accrued Loss Reserves - Noncurrent	3,513	3,401
Accrued environmental reserves
Schedule Of Accrued Liabilities [Line Items]
Accrued losses	1,970	1,147
Accrued Loss Reserves - Noncurrent	$ 4,125	$ 4,211