Fair Value and Carrying Value of Financial Instruments and Long-Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	Feb. 28, 2014	May 31, 2013	Feb. 28, 2013	May 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, carrying value	$ 216,001	$ 343,554	$ 247,104	$ 315,968
Marketable equity securities, carrying value	91,800	90,292
Marketable debt securities, carrying value	20,314	22,801
Long-term debt, including current portion, carrying value	1,388,435	1,373,697
Cash and cash equivalents, fair value	216,001	343,554
Marketable securities, fair value	112,114	113,093
Long-term debt, including current portion, fair value	1,531,086	1,501,850
Equity securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities, fair value	91,800	90,292
Fixed securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities, fair value	$ 20,314	$ 22,801