Fair Value and Carrying Value of Financial Instruments and Long-Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	Nov. 30, 2013	May 31, 2013	Nov. 30, 2012	May 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, carrying value	$ 224,172	$ 343,554	$ 261,940	$ 315,968
Marketable equity securities, carrying value	113,663	90,292
Marketable debt securities, carrying value	21,561	22,801
Long-term debt, including current portion, carrying value	1,369,950	1,373,697
Cash and cash equivalents, fair value	224,172	343,554
Marketable securities, fair value	135,224	113,093
Long-term debt, including current portion, fair value	1,452,556	1,501,850
Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities, fair value	113,663	90,292
Fixed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities, fair value	$ 21,561	$ 22,801