Assets and Liabilities that are Measured at Fair Value on Recurring Basis and are Categorized using Fair Value Hierarchy (Detail) (Fair Value, Measurements, Recurring, USD $) In Thousands, unless otherwise specified	Feb. 29, 2012	May 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets (liabilities) at fair value	$ 102,208	$ 135,281
Foreign currency forward contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts, fair value of liability	(752)
Foreign currency contracts, fair value of assets		6,157
Cross-currency swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts, fair value of liability	(13,626)	(20,519)
Kemrock Industries and Exports Limited
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	7,086
Fixed maturity | U.S. Treasury and other government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	19,403	26,480
Fixed maturity | Foreign bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	39
Fixed maturity | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	349	532
Fixed maturity | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	2,693	3,029
Equity securities | Stocks | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	1,281	37,549
Equity securities | Stocks | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	27,588	31,849
Equity securities | Mutual funds | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	17,876	18,413
Equity securities | Mutual funds | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	40,271	31,791
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets (liabilities) at fair value	35,955	69,398
Quoted Prices in Active Markets for Identical Assets (Level 1) | Kemrock Industries and Exports Limited
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	7,086
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities | Stocks | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	1,281	37,549
Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities | Stocks | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	27,588	31,849
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets (liabilities) at fair value	66,253	65,883
Significant Other Observable Inputs (Level 2) | Foreign currency forward contract
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts, fair value of liability	(752)
Foreign currency contracts, fair value of assets		6,157
Significant Other Observable Inputs (Level 2) | Cross-currency swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts, fair value of liability	(13,626)	(20,519)
Significant Other Observable Inputs (Level 2) | Fixed maturity | U.S. Treasury and other government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	19,403	26,480
Significant Other Observable Inputs (Level 2) | Fixed maturity | Foreign bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	39
Significant Other Observable Inputs (Level 2) | Fixed maturity | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	349	532
Significant Other Observable Inputs (Level 2) | Fixed maturity | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	2,693	3,029
Significant Other Observable Inputs (Level 2) | Equity securities | Mutual funds | Foreign
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	17,876	18,413
Significant Other Observable Inputs (Level 2) | Equity securities | Mutual funds | Domestic
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	$ 40,271	$ 31,791