Components of Net Postretirement Expense (Detail) - Postretirement Benefits - USD ($) $ in Thousands	12 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2018
Domestic
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost on the accumulated obligation	$ 149	$ 192	$ 173
Prior service (credit)	(219)	(219)	(220)
Net actuarial (gains) losses	(66)	(26)	24
Net Pension Cost	(136)	(53)	(23)
Non-U.S. Plans
Defined Benefit Plans And Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost - benefits earned during the period	1,661	1,507	1,307
Interest cost on the accumulated obligation	1,089	1,122	939
Net actuarial (gains) losses	611	442	332
Net Pension Cost	$ 3,361	$ 3,071	$ 2,578