Restructuring and Other Expense - Additional Information (Detail) - USD ($)	3 Months Ended
	Aug. 31, 2017	Aug. 31, 2016
Restructuring Cost and Reserve [Line Items]
Net gain (loss) on sale of assets	$ 1,425,000	$ 4,396,000
AMTROL
Restructuring Cost and Reserve [Line Items]
Severance expense	1,877,000
Other Non-significant Restructuring Activities
Restructuring Cost and Reserve [Line Items]
Facility exit costs	5,000
Net gain (loss) on sale of assets	143,000
Closure of Precision Specialty Metals, Inc
Restructuring Cost and Reserve [Line Items]
Facility exit costs	$ 279,000