Employee Benefit Plans - Components of Net Periodic Pension (Benefit) Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2020	May 31, 2019
Retirement Benefits [Abstract]
Interest cost	$ 2,881	$ 3,124
Expected return on assets	(2,961)	(2,882)
Net periodic pension (benefit) cost	$ (80)	$ 242