Investment in Kemrock Industries and Exports Ltd - Additional Information (Detail)	3 Months Ended			3 Months Ended	12 Months Ended		12 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended
	Aug. 31, 2012 USD ($)	Aug. 31, 2012 INR	May 31, 2012 INR	Aug. 31, 2012 Kemrock Industries and Exports Limited USD ($)	May 31, 2012 Kemrock Industries and Exports Limited USD ($)	May 31, 2011 Kemrock Industries and Exports Limited	May 31, 2012 Kemrock global depository receipts USD ($)	Apr. 30, 2012 Conversion option, Kemrock 5.5% bonds USD ($)	Aug. 31, 2012 Conversion option, Kemrock 5.5% bonds	May 31, 2012 Conversion option, Kemrock 5.5% bonds USD ($)	Apr. 30, 2012 Conversion option, Kemrock 5.5% bonds Minimum	May 31, 2012 Conversion option, Kemrock 5.5% bonds Minimum	Apr. 30, 2012 Conversion option, Kemrock 5.5% bonds Maximum	May 31, 2012 Conversion option, Kemrock 5.5% bonds Maximum
Basis of Presentation [Line Items]
Advances to affiliate					$ 15,000,000
Agreement expiration period					Sep. 15, 2012
Acquisition of equity method investment, shares					870,000	3,200,000	693,072
Purchase of global depository receipt, value							7,200,000
Equity method investment carrying value							42,200,000
Investment in affiliate								22,700,000		22,700,000
Investment in affiliate, interest rate								5.50%	5.50%	5.50%
Debt securities, conversion date											Jun. 04, 2012	Jun. 04, 2012	Jun. 12, 2017	Jun. 12, 2017
Kemrock common stock market value per share		116.6	531.0
Impairment loss on equity method investment	(32,100,000)
Proceeds from affiliate				5,000,000
Loans deemed uncollectible, recorded as loss				5,000,000
Loss on Kemrock conversion option	$ (8,183,000)