Changes In Equity (Schedule Of Changes In Total Equity, Shareholders' Equity Attributable To Controlling Interest, And Equity Attributable To Noncontrolling Interest) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2011		Nov. 30, 2010
Schedule of Capitalization, Equity [Line Items]
Balance, Beginning			$ 740,703
Comprehensive income			30,337	[1]
Common shares issued	8,523		8,523
Stock-based compensation			6,274
Purchases and retirement of common shares			(52,120)
Dividends paid to noncontrolling interest	(3,456)	(3,457)	(6,576)		(6,577)
Cash dividends declared			(16,799)
Balance, Ending	710,342		710,342
Additional Paid-In Capital [Member]
Schedule of Capitalization, Equity [Line Items]
Balance, Beginning			181,525
Common shares issued	8,523		8,523
Stock-based compensation			6,274
Purchases and retirement of common shares			(8,672)
Balance, Ending	187,650		187,650
Cumulative Other Comprehensive Income (Loss), Net Of Tax [Member]
Schedule of Capitalization, Equity [Line Items]
Balance, Beginning			3,975
Comprehensive income			(9,863)	[1]
Balance, Ending	(5,888)		(5,888)
Retained Earnings [Member]
Schedule of Capitalization, Equity [Line Items]
Balance, Beginning			504,410
Comprehensive income			37,637	[1]
Purchases and retirement of common shares			(43,448)
Cash dividends declared			(16,799)
Balance, Ending	481,800		481,800
Total [Member]
Schedule of Capitalization, Equity [Line Items]
Balance, Beginning			689,910
Comprehensive income			27,774	[1]
Common shares issued	8,523		8,523
Stock-based compensation			6,274
Purchases and retirement of common shares			(52,120)
Cash dividends declared			(16,799)
Balance, Ending	663,562		663,562
Non-Controlling Interest [Member]
Schedule of Capitalization, Equity [Line Items]
Balance, Beginning			50,793
Comprehensive income			2,563	[1]
Dividends paid to noncontrolling interest			(6,576)
Balance, Ending	$ 46,780		$ 46,780

[1] The allocation of the components of comprehensive income attributable to controlling and noncontrolling interests is disclosed in "NOTE G - Comprehensive Income."