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, 2019	May 31, 2018	May 31, 2017
Change in benefit obligation
Benefit obligation, beginning of year	$ 38,010	$ 39,174
Interest cost	1,503	1,522	$ 1,527
Actuarial (gain) loss	1,868	(1,516)
Benefits paid	(1,201)	(1,170)
Settlements	(1,661)
Benefits obligation, end of year	38,519	38,010	39,174
Change in plan assets
Fair value, beginning of year	27,212	27,022
Return on plan assets	532	1,361	2,224
Company contributions	1,376
Benefits paid	(1,201)	(1,171)
Settlements	(1,661)
Fair value, end of year	26,258	27,212	$ 27,022
Funded status	(12,261)	(10,798)
Amounts recognized in accumulated other comprehensive loss consist of:
Net loss	18,370	16,343
Other Liabilities
Amounts recognized in the consolidated balance sheets consist of:
Amounts recognized in the consolidated balance sheets	(12,261)	(10,798)
Amounts recognized in accumulated other comprehensive loss consist of:
Total	(12,261)	(10,798)
Accumulated Other Comprehensive Loss
Amounts recognized in the consolidated balance sheets consist of:
Amounts recognized in the consolidated balance sheets	18,370	16,343
Amounts recognized in accumulated other comprehensive loss consist of:
Total	$ 18,370	$ 16,343