OTHER (INCOME), NET - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2011	Nov. 30, 2010	Sep. 30, 2011	May 31, 2011
Schedule of Equity Method Investments [Line Items]
Acquisition of Kemrock common stock equity, shares					870,000	3,200,000
Kemrock common stock equity, carrying value	$ 34,600,000		$ 34,600,000			$ 24,200,000
Ownership percentage in Kemrock Industrial and Exports Limited					23.00%	18.00%
Fair market value of investment in Kemrock						35,800,000
Net earnings	49,931,000	48,791,000	126,742,000	117,787,000
Other Investments
Schedule of Equity Method Investments [Line Items]
Net earnings	$ 5,200,000	$ 4,600,000