Schedule of Progression of Liabilities Associated with Restructuring Activities, Combined with Reconciliation to Restructuring and Other Expense (Income) (Detail) (USD $)	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 6,229,000	$ 5,583,000
Expense/ (Income)	8,713,000	4,575,000
Payments	(7,724,000)	(4,766,000)
Adjustments	(189,000)	837,000
Ending Balance	7,029,000	6,229,000	5,583,000
Net gain on sale of assets	(10,589,000)	(1,886,000)
Less: joint venture transactions	(1,036,000)	604,000	150,000
Restructuring and other expense (income)	(2,912,000)	3,293,000	5,984,000
Early Retirement And Severance
Restructuring Cost and Reserve [Line Items]
Beginning Balance	5,029,000	4,892,000
Expense/ (Income)	6,236,000	2,228,000
Payments	(4,703,000)	(2,388,000)
Adjustments	(67,000)	297,000
Ending Balance	6,495,000	5,029,000
Facility Exit And Other Costs
Restructuring Cost and Reserve [Line Items]
Beginning Balance	1,200,000	691,000
Expense/ (Income)	2,477,000	2,347,000
Payments	(3,021,000)	(2,378,000)
Adjustments	(122,000)	540,000
Ending Balance	$ 534,000	$ 1,200,000