Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	May 31, 2019	May 31, 2018
Deferred tax assets
Accounts receivable	$ 1,516	$ 1,455
Inventories	5,649	5,004
Accrued expenses	21,195	23,219
Net operating loss carry forwards	16,433	14,201
Stock-based compensation	10,989	10,588
Derivative contracts	2,054
Other	316	1,313
Total deferred tax assets	58,152	55,780
Valuation allowance for deferred tax assets	(14,619)	(14,006)
Net deferred tax assets	43,533	41,774
Deferred tax liabilities
Property, plant and equipment	(91,732)	(74,512)
Investment in affiliated companies, principally due to undistributed earnings	(23,035)	(22,918)
Derivative contracts		(2,653)
Other	(2,868)	(1,879)
Total deferred tax liability	(117,635)	(101,962)
Net deferred tax liability	$ (74,102)	$ (60,188)