Assets Measured at Fair Value on Non-Recurring Basis (Parenthetical) (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Nov. 30, 2017	Nov. 30, 2017	May 31, 2017
Fair Value [Line Items]
Impairment of long-lived assets	$ 8,289,000	$ 8,289,000
Assets estimated fair value	100,000	100,000	$ 0
WEI Reporting Unit
Fair Value [Line Items]
Impairment of long-lived assets	7,325,000
Assets estimated fair value	0	0
Bremen, Ohio
Fair Value [Line Items]
Impairment of long-lived assets	964,000
Assets estimated fair value	$ 100,000	$ 100,000