Schedule of Progression of Liabilities Associated with Restructuring Activities, Combined with Reconciliation to Restructuring and Other Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2014	Nov. 30, 2013	Nov. 30, 2014	Nov. 30, 2013
Restructuring Cost and Reserve [Line Items]
Beginning Balance			$ 7,029
Expense (Income)			588
Payments			(4,784)
Adjustments			240
Ending Balance	3,073		3,073
Less: joint venture transactions	(83)	(786)	(190)	(928)
Restructuring and other expense	405	(1,182)	398	(5,179)
Early Retirement And Severance
Restructuring Cost and Reserve [Line Items]
Beginning Balance			6,495
Expense (Income)			(30)
Payments			(3,852)
Adjustments			30
Ending Balance	2,643		2,643
Facility Exit And Other Costs
Restructuring Cost and Reserve [Line Items]
Beginning Balance			534
Expense (Income)			618
Payments			(932)
Adjustments			210
Ending Balance	$ 430		$ 430