Employee Pension Plans - Reconciliation of Changes in Projected Benefit Obligation and Fair Value of Plan Assets and Funded Status of Gerstenslager Plan (Detail) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2019
Change in benefit obligation
Benefit obligation, beginning of year	$ 46,167	$ 38,519
Interest cost	1,205	1,352	$ 1,503
Actuarial (gain) loss	(4,814)	7,671
Benefits paid	(1,345)	(1,375)
Settlements	(18)
Benefits obligation, end of year	41,195	46,167	38,519
Change in plan assets
Fair value, beginning of year	28,510	26,258
Return on plan assets	4,289	1,928	532
Company contributions	1,700	1,699
Benefits paid	(1,345)	(1,375)
Settlements	(18)
Fair value, end of year	33,136	28,510	$ 26,258
Funded status	(8,059)	(17,657)
Amounts recognized in accumulated other comprehensive loss consist of:
Net loss	17,541	25,413
Other Liabilities
Amounts recognized in the consolidated balance sheets consist of:
Amounts recognized in the consolidated balance sheets	(8,059)	(17,657)
Amounts recognized in accumulated other comprehensive loss consist of:
Total	(8,059)	(17,657)
Accumulated Other Comprehensive Loss
Amounts recognized in the consolidated balance sheets consist of:
Amounts recognized in the consolidated balance sheets	17,541	25,413
Amounts recognized in accumulated other comprehensive loss consist of:
Total	$ 17,541	$ 25,413