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, 2020	May 31, 2019	May 31, 2018
Change in benefit obligation
Benefit obligation, beginning of year	$ 38,519	$ 38,010
Interest cost	1,352	1,503	$ 1,522
Actuarial loss	7,671	1,868
Benefits paid	(1,375)	(1,201)
Settlements		(1,661)
Benefits obligation, end of year	46,167	38,519	38,010
Change in plan assets
Fair value, beginning of year	26,258	27,212
Return on plan assets	1,928	532	1,361
Company contributions	1,699	1,376
Benefits paid	(1,375)	(1,201)
Settlements		(1,661)
Fair value, end of year	28,510	26,258	$ 27,212
Funded status	(17,657)	(12,261)
Amounts recognized in accumulated other comprehensive loss consist of:
Net loss	25,413	18,370
Other Liabilities
Amounts recognized in the consolidated balance sheets consist of:
Amounts recognized in the consolidated balance sheets	(17,657)	(12,261)
Amounts recognized in accumulated other comprehensive loss consist of:
Total	(17,657)	(12,261)
Accumulated Other Comprehensive Loss
Amounts recognized in the consolidated balance sheets consist of:
Amounts recognized in the consolidated balance sheets	25,413	18,370
Amounts recognized in accumulated other comprehensive loss consist of:
Total	$ 25,413	$ 18,370