Consolidated Statements of Shareholders' Equity (USD $) In Thousands	Total	Common Stock	Paid-In Capital	Retained Earnings	Other Accumulated Comprehensive Income (Loss)	Treasury Stock	Comprehensive Income
Balance at May. 31, 2008	$ 2,254,131	$ 129,182	$ 60,408	$ 2,784,302	$ 52,280	$ (772,041)
Balance (in shares) at May. 31, 2008		173,083				(19,392)
Increase (Decrease) in Shareholders' Equity
Net income	226,357			226,357			226,357
Equity adjustment for foreign currency translation	(27,701)				(27,701)		(27,701)
Change in fair value of derivatives, net of $3,813, ($260) and $94 of tax expense (benefit) for the year ended May 31, 2011, 2010 and 2009, respectively	(159)				(159)		(159)
Amortization of interest rate lock agreements	767				767		767
Change in fair value of available-for-sale securities, net of $0, ($14) and $50 of tax expense (benefit) for the year ended May 31, 2011, 2010 and 2009, respectively	112				112		112
Comprehensive income, net of tax	199,376						199,376
Dividends	(72,207)			(72,207)
Stock-based compensation	11,953		11,953
Stock options exercised, net of shares surrendered (in shares)		3
Repurchase of common stock	(25,847)					(25,847)
Repurchase of common stock (in shares)						(904)
Other	3	33	3	(33)
Balance at May. 31, 2009	2,367,409	129,215	72,364	2,938,419	25,299	(797,888)
Balance (in shares) at May. 31, 2009		173,086				(20,296)
Increase (Decrease) in Shareholders' Equity
Net income	215,620			215,620			215,620
Equity adjustment for foreign currency translation	9,365				9,365		9,365
Change in fair value of derivatives, net of $3,813, ($260) and $94 of tax expense (benefit) for the year ended May 31, 2011, 2010 and 2009, respectively	443				443		443
Amortization of interest rate lock agreements	767				767		767
Change in fair value of available-for-sale securities, net of $0, ($14) and $50 of tax expense (benefit) for the year ended May 31, 2011, 2010 and 2009, respectively	(28)				(28)		(28)
Comprehensive income, net of tax	226,167						226,167
Dividends	(73,960)			(73,960)
Stock-based compensation	15,349		15,349
Vesting of stock-based compensation awards		2,843	(2,843)
Vesting of stock-based compensation awards (in shares)		121
Repurchase of common stock	(969)					(969)
Repurchase of common stock (in shares)						(42)
Other	33		(254)		287
Balance at May. 31, 2010	2,534,029	132,058	84,616	3,080,079	36,133	(798,857)
Balance (in shares) at May. 31, 2010		173,207				(20,338)
Increase (Decrease) in Shareholders' Equity
Net income	246,989			246,989			246,989
Equity adjustment for foreign currency translation	27,344				27,344		27,344
Change in fair value of derivatives, net of $3,813, ($260) and $94 of tax expense (benefit) for the year ended May 31, 2011, 2010 and 2009, respectively	(6,096)				(6,096)		(6,096)
Amortization of interest rate lock agreements	767				767		767
Change in fair value of available-for-sale securities, net of $0, ($14) and $50 of tax expense (benefit) for the year ended May 31, 2011, 2010 and 2009, respectively	3				3		3
Comprehensive income, net of tax	269,007						269,007
Dividends	(71,812)			(71,812)
Stock-based compensation	15,203		15,203
Vesting of stock-based compensation awards		3,343	(3,343)
Vesting of stock-based compensation awards (in shares)		139
Repurchase of common stock	(443,690)					(443,690)
Repurchase of common stock (in shares)						(15,424)
Other	(88)		(744)		656
Balance at May. 31, 2011	$ 2,302,649	$ 135,401	$ 95,732	$ 3,255,256	$ 58,807	$ (1,242,547)
Balance (in shares) at May. 31, 2011		173,346				(35,762)