Employee Pension Plans - Additional Information (Detail) (USD $)	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Estimated net gain	$ 327,208
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; (ii) to earn nominal returns, net of investment fees, equal to or in excess of the actuarial assumptions of the plan; and (iii) to include a strategic asset allocation of 60-80% equities, including international, and 20-40% fixed income investments.
Weighted-average asset allocation	100.00%	100.00%
Expected employer contribution to defined benefit plan during fiscal 2014	824,602
Net periodic pension costs	(248,000)	194,000	(332,000)
Assumed salary rate increase
Discount rate	4.44%	4.16%	5.60%
Fixed Income Investments | Minimum
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation	20.00%
Fixed Income Investments | Maximum
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation	40.00%
Austrian Pressure Cylinders
Defined Benefit Plan Disclosure [Line Items]
Accrued liability of unfunded plans included in other liabilities	6,440,000	6,074,000
Net periodic pension costs	$ 677,000	$ 689,000	$ 623,000
Assumed salary rate increase	3.00%	3.00%	3.00%
Discount rate	3.25%	4.50%	4.50%
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation	52.00%	70.00%
Equity Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation	60.00%
Equity Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Weighted-average asset allocation	80.00%