Other Expense (Income), Net - Additional Information (Detail) (USD $)	3 Months Ended			6 Months Ended	9 Months Ended	1 Months Ended	6 Months Ended	12 Months Ended				12 Months Ended
	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	Nov. 30, 2012	Feb. 28, 2013	Apr. 30, 2012 Conversion option, Kemrock 5.5% bonds	Nov. 30, 2012 Conversion option, Kemrock 5.5% bonds	May 31, 2012 Conversion option, Kemrock 5.5% bonds	Feb. 28, 2013 Kemrock Industries and Exports Limited	May 31, 2012 Kemrock Industries and Exports Limited	May 31, 2011 Kemrock Industries and Exports Limited	May 31, 2012 Kemrock global depository receipts
Component of Other Income, Nonoperating [Line Items]
Acquisition of equity method investment, shares										870,000	3,200,000	693,072
Equity method investment, carrying value									$ 0	$ 42,200,000	$ 24,200,000
Equity method investment, ownership percentage										23.00%	18.00%
Purchase of global depository receipt, value												7,200,000
Investment in affiliate						22,700,000		22,700,000
Investment in affiliate, interest rate						5.50%	5.50%	5.50%
Impairment loss on equity method investment		(10,100,000)	(32,100,000)	(42,200,000)
Loss on Kemrock conversion option		(800,000)	(8,200,000)	(9,000,000)	(9,030,000)
Loss on Brazil operational repositioning	$ 6,087,000				$ 6,087,000