Pretax Net Actuarial Loss, Prior Service (Cost) and Transition Assets/(Obligation) Recognized in Accumulated Other Comprehensive Income (Loss) not Affecting Retained Earnings, Postretirement (Detail) - Postretirement Benefits - USD ($) $ in Thousands	May 31, 2020	May 31, 2019
Domestic
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net actuarial gain (loss)	$ (386)	$ 381
Prior service credits	448	667
Total recognized in accumulated other comprehensive income not affecting retained earnings	62	1,048
Non-U.S. Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net actuarial gain (loss)	(11,331)	(12,891)
Total recognized in accumulated other comprehensive income not affecting retained earnings	$ (11,331)	$ (12,891)