Fair Value Measurements - Additional Information (Detail)	3 Months Ended	6 Months Ended				1 Months Ended	6 Months Ended	12 Months Ended	3 Months Ended
	Nov. 30, 2012 USD ($)	Nov. 30, 2012 USD ($)	Nov. 30, 2012 EUR (€)	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	Nov. 30, 2012 Unsecured Senior Notes	Nov. 30, 2012 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										$ 10,638,000	$ 2,159,000
Debt, interest rate									6.70%
Debt, due date									Nov. 01, 2015
Effective euro fixed-rate borrowing	5.31%	5.31%
Notional principal amount of cross-currency swap	150,000,000	150,000,000	125,000,000
Loss on Kemrock conversion option	$ (847,000)	$ (9,030,000)
Investment in affiliate, interest rate						5.50%	5.50%	5.50%
Kemrock common stock market value per share				56.70	531.00