Employee Benefit Plans - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Accrued benefit liability	$ 21,500	$ 37,000
Unrecognized net actuarial loss	$ 5,000	$ 16,200
Expected return on plan assets	4.25%	4.80%
Expected contributions next twelve months	$ 300
Expected contributions in year one	4,100
Expected contributions in year two	4,200
Expected contributions in year three	4,400
Expected contributions in year four	4,500
Expected contributions in year five	4,700
Expected contributions thereafter	25,000
Fair value of plan assets	78,244	$ 68,341	$ 62,267
Projected benefit obligation	99,728	105,357	91,935
Employer contributions	3,613	2,098
Supplemental Executive Retirement Plan (SERP)
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 9,100	8,400	8,600
United States Plan
Defined Benefit Plan Disclosure [Line Items]
Required years of service for plan eligibility	1 year
Employer contributions	$ 75,600	74,300	67,600
Canada | DPSP and RRSP
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	3,100	2,600	$ 2,500
Pension Plan of Immaterial Acquisitions
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9,200	7,300
Projected benefit obligation	$ 8,900	$ 9,400