Other Expense (Income), Net - Additional Information (Detail) In Millions, except Share data, unless otherwise specified	3 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 ($)	May 31, 2011 Kemrock Industries and Exports Limited USD ($)	May 31, 2012 Kemrock global depository receipts USD ($)
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				$ 10.0	$ 42.2	$ 24.2
Equity method investment, ownership percentage					23.00%	18.00%
Purchase of global depository receipt, value							7.2
Kemrock common stock market value per share		116.6	531.0
Impairment loss on equity method investment	$ 32.1