Schedule of Progression of Liabilities Created as Part of Transformation Plan, Combined with Reconciliation to Restructuring and Other Expense (Detail) (USD $)	3 Months Ended		9 Months Ended
	Feb. 28, 2013	Feb. 29, 2012	Feb. 28, 2013	Feb. 29, 2012
Restructuring Cost and Reserve [Line Items]
Beginning Balance			$ 5,583,000
Expense/ (Income)			2,509,000
Payments			(3,345,000)
Adjustments			(163,000)
Ending Balance	4,584,000		4,584,000
Net gain on asset disposals	(1,886,000)		(1,886,000)
Less: joint venture transactions			1,188,000
Restructuring and other expense	146,000	956,000	1,811,000	4,707,000
Early Retirement And Severance
Restructuring Cost and Reserve [Line Items]
Beginning Balance			4,892,000
Expense/ (Income)			(254,000)
Payments			(1,756,000)
Adjustments			297,000
Ending Balance	3,179,000		3,179,000
Facility Exit And Other Costs
Restructuring Cost and Reserve [Line Items]
Beginning Balance			691,000
Expense/ (Income)			2,763,000
Payments			(1,589,000)
Adjustments			(460,000)
Ending Balance	$ 1,405,000		$ 1,405,000