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Employee Pension Plans - Additional Information (Detail)
12 Months Ended
May 31, 2018
USD ($)
DefinedBenefitPlan
May 31, 2017
USD ($)
May 31, 2016
USD ($)
Defined Benefit Plan Disclosure [Line Items]      
Estimated net loss $ 441,000    
Description of investment policy and strategy for the defined benefit plan The investment policy and strategy for the defined benefit plan is: (i) long-term in nature with liquidity requirements that are anticipated to be minimal due to the projected normal retirement date of the average employee and the current average age of participants;    
Employer contribution to defined benifit plan in fiscal 2019 $ 104,000    
Number of planned contributions in fiscal 2019 | DefinedBenefitPlan 5    
Expected employer contribution to defined benefit plan during fiscal 2019 $ 876,000    
Net periodic pension costs $ 141,000 $ 328,000 $ 111,000
Assumed salary rate increase 0.00% 0.00% 0.00%
Discount rate 3.94% 3.75% 4.07%
Austrian Pressure Cylinders      
Defined Benefit Plan Disclosure [Line Items]      
Accrued liability of unfunded plans included in other liabilities $ 6,561,000 $ 6,149,000  
Net periodic pension costs $ 601,000 $ 554,000 $ 617,000
Assumed salary rate increase 2.75% 2.75% 2.75%
Discount rate 1.80% 1.60% 1.75%