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, 2019	May 31, 2018	May 31, 2017
Compensation And Retirement Disclosure [Abstract]
Interest cost	$ 1,503	$ 1,522	$ 1,527
Return on plan assets	(532)	(1,361)	(2,224)
Net amortization and deferral	(918)	(20)	1,025
Net periodic pension cost on defined benefit plan	53	141	328
Settlement cost	760
Defined contribution plans	16,308	14,972	14,542
Total retirement plan cost	$ 17,121	$ 15,113	$ 14,870