Investment in Kemrock Industries and Exports Ltd - Additional Information (Detail)	3 Months Ended	6 Months Ended	9 Months Ended					3 Months Ended	12 Months Ended			12 Months Ended
	Nov. 30, 2012 USD ($)	Nov. 30, 2012 USD ($)	Feb. 28, 2013 USD ($)	May 31, 2013 INR	Nov. 30, 2012 INR	Aug. 08, 2012	May 31, 2012 INR	Aug. 31, 2012 Kemrock Industries and Exports Limited USD ($)	May 31, 2013 Kemrock Industries and Exports Limited USD ($)	May 31, 2012 Kemrock Industries and Exports Limited USD ($)	May 31, 2011 Kemrock Industries and Exports Limited USD ($)	May 31, 2012 Kemrock global depository receipts USD ($)	May 31, 2012 Conversion option, Kemrock 5.5% bonds USD ($)	May 31, 2013 Conversion option, Kemrock 5.5% bonds Kemrock Industries and Exports Limited USD ($)	May 31, 2013 Embedded Conversion Feature Kemrock Industries and Exports Limited USD ($)
Basis of Presentation [Line Items]
Acquisition of equity method investment, shares											3,200,000	693,072
Equity method investment, carrying value											$ 24,200,000	$ 42,200,000
Equity method investment, ownership percentage											18.00%
Advances to affiliate								10,000,000		15,000,000
Agreement expiration period										Sep. 15, 2012
Purchase of global depository receipt, value												7,200,000
Investment in affiliate													22,700,000
Investment in affiliate, interest rate													5.50%
Kemrock common stock market value per share				43.85	56.70		531.00
Kemrock common stock price declining percentage						40.00%
Impairment loss on equity method investment	10,100,000	42,200,000
Loans deemed uncollectible, recorded as loss								5,000,000
Loss on Kemrock conversion option	800,000	9,000,000	9,030,000
Impairment on investment in Kemrock			$ 51,092,000						$ 42,200,000					$ 13,700,000	$ 9,000,000