Components of Net Deferred Tax Liability (Detail) (USD $) In Thousands, unless otherwise specified	May 31, 2012	May 31, 2011
Deferred tax assets
Deferred compensation	$ 22,626	$ 22,341
Inventory costs	4,897	6,833
Accrued expenses not currently tax deductible	9,192	10,205
Goodwill	988	2,191
Other comprehensive income	11,042	7,250
Alternative minimum tax credit carryforward	28,808	28,808
Net operating loss carryforward	61,530	49,896
Other	5,998	4,803
Total deferred tax assets	145,081	132,327
Valuation allowance	(5,159)
Net deferred tax assets	139,922	132,327
Deferred tax liabilities
Property, plant and equipment	103,583	99,750
Deferred real estate gains	19,049	14,505
Other	3,575	3,039
Total deferred tax liabilities	126,207	117,294
Net deferred tax asset	13,715	15,033
Less current deferred tax asset	10,713	12,346
Long-term deferred tax asset	$ 3,002	$ 2,687