Assets and Liabilities that are Measured at Fair Value on a Recurring Basis and are Categorized Using the Fair Value Hierarchy (Detail) (Fair Value, Measurements, Recurring, USD $) In Thousands	Aug. 31, 2011	May 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets (liabilities) at fair value	$ 123,157	$ 135,281
Equity securities | Stocks | Foreign | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	37,693	37,549
Equity securities | Stocks | Domestic | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	31,596	31,849
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets (liabilities) at fair value	69,289	69,398
Equity securities | Mutual funds | Foreign | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	16,092	18,413
Equity securities | Mutual funds | Domestic | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	25,995	31,791
Fixed maturity | U.S. Treasury and other government | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	25,270	26,480
Fixed maturity | Corporate bonds | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	2,967	3,029
Fixed maturity | Foreign bonds | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	37
Fixed maturity | Mortgage-backed securities | Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	338	532
Significant Other Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets (liabilities) at fair value	53,868	65,883
Significant Other Observable Inputs (Level 2) | Foreign Currency Forward Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	6,279	6,157
Significant Other Observable Inputs (Level 2) | Cross-currency swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities measured at fair value on a recurring basis	(23,110)	(20,519)
Equity securities | Stocks | Foreign
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	37,693	37,549
Equity securities | Stocks | Domestic
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	31,596	31,849
Equity securities | Mutual funds | Foreign
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	16,092	18,413
Equity securities | Mutual funds | Domestic
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	25,995	31,791
Fixed maturity | U.S. Treasury and other government
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	25,270	26,480
Fixed maturity | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	2,967	3,029
Fixed maturity | Foreign bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	37
Fixed maturity | Mortgage-backed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	338	532
Foreign Currency Forward Contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets measured at fair value on a recurring basis	6,279	6,157
Cross-currency swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities measured at fair value on a recurring basis	$ (23,110)	$ (20,519)