Fair Value Measurements - Additional Information (Detail)	3 Months Ended		6 Months Ended	9 Months Ended					1 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended
	Nov. 30, 2012 USD ($)	Aug. 31, 2012 USD ($)	Nov. 30, 2012 USD ($)	Feb. 28, 2013 USD ($)	Feb. 28, 2013 EUR (€)	Feb. 28, 2013 INR	Nov. 30, 2012 INR	May 31, 2012 INR	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 Unsecured Senior Notes	Feb. 28, 2013 Fair Value, Measurements, Recurring Cross-currency swap USD ($)	May 31, 2012 Fair Value, Measurements, Recurring Cross-currency swap USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts, fair value of liability													$ 10,949,000	$ 2,159,000
Debt, interest rate												6.70%
Debt, due date												Nov. 01, 2015
Effective euro fixed-rate borrowing				5.31%
Notional principal amount of cross-currency swap				150,000,000	125,000,000
Loss on Kemrock conversion option	$ 800,000	$ 8,200,000	$ 9,000,000	$ (9,030,000)
Investment in affiliate, interest rate									5.50%	5.50%	5.50%
Kemrock common stock market value per share						52.90	56.70	531.00