Employee Pension Plans - Components of Net Periodic Pension Cost for the Defined Benefit Plan and Defined Contribution Plans (Detail) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2018
Compensation And Retirement Disclosure [Abstract]
Interest cost	$ 1,352	$ 1,503	$ 1,522
Return on plan assets	(1,928)	(532)	(1,361)
Net amortization and deferral	628	(918)	(20)
Net periodic pension cost on defined benefit plan	52	53	141
Settlement cost		760
Defined contribution plans	16,495	16,308	14,972
Total retirement plan cost	$ 16,547	$ 17,121	$ 15,113