Employee Benefit Plans - Obligations and Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2021	May 31, 2020
Change in benefit obligation:
Projected benefit obligation, beginning of year	$ 105,357	$ 91,935
Interest cost	2,050	2,881
Actuarial (gain) loss	(4,460)	13,662
Benefits paid	(3,219)	(3,121)
Projected benefit obligation, end of year	99,728	105,357
Change in plan assets:
Fair value of plan assets, beginning of year	68,341	62,267
Actual return on plan assets	9,509	7,097
Employer contributions	3,613	2,098
Benefits paid	(3,219)	(3,121)
Fair value of plan assets, end of year	78,244	68,341
Funded status-net amount recognized	$ (21,484)	$ (37,016)