Restructuring and Other Expense (Income), Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2016
Restructuring Cost and Reserve [Line Items]
Net gain (loss) on sale of assets	$ 10,522	$ (7,951)	$ 12,996
Closure of Precision Specialty Metals, Inc
Restructuring Cost and Reserve [Line Items]
Facility exit costs	560
Net gain (loss) on sale of assets	10,595
Cash proceeds from sale of business	15,874
Other Non-significant Restructuring Activities
Restructuring Cost and Reserve [Line Items]
Severance expense	184
Net gain (loss) on sale of assets	(143)
Facility exit costs credit	78
AMTROL
Restructuring Cost and Reserve [Line Items]
Severance expense	$ 2,365