Schedule of Progression of Liabilities Created as Part of Transformation Plan, Combined with Reconciliation to Restructuring and Other Expense (Detail) (USD $)	3 Months Ended
	Aug. 31, 2012	Aug. 31, 2011
Restructuring Cost and Reserve [Line Items]
Beginning Balance	$ 5,583,000
Expense	399,000
Payments	(1,010,000)
Adjustments	(336,000)
Ending Balance	4,636,000
Net gain on asset disposals	(1,158,000)
Less: joint venture transactions	1,162,000
Restructuring and other expense	403,000	1,703,000
Early Retirement And Severance
Restructuring Cost and Reserve [Line Items]
Beginning Balance	4,892,000
Expense	(165,000)
Payments	(510,000)
Adjustments	(3,000)
Ending Balance	4,214,000
Facility Exit And Other Costs
Restructuring Cost and Reserve [Line Items]
Beginning Balance	691,000
Expense	564,000
Payments	(500,000)
Adjustments	(333,000)
Ending Balance	$ 422,000