Restructuring and Other Expense - Additional Information (Detail)	3 Months Ended
	Aug. 31, 2015 USD ($)
Engineered Cabs
Restructuring Cost and Reserve [Line Items]
Severance expense	$ 1,891,000
Aluminum High Pressure Cylinder Business
Restructuring Cost and Reserve [Line Items]
Severance expense	$ 690,000
Production ceased date	Sep. 22, 2015