Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	May 31, 2013	Feb. 28, 2013	Nov. 30, 2012	Aug. 31, 2012	May 31, 2012	Feb. 29, 2012	Nov. 30, 2011	Aug. 31, 2011	May 31, 2013		May 31, 2012		May 31, 2011
Statement of Other Comprehensive Income [Abstract]
Net income	$ 85,977	$ 74,705	$ 78,027	$ 76,733	$ 78,614	$ 76,035	$ 74,350	$ 68,638	$ 315,442		$ 297,637		$ 246,989
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments									(1,087)		(17,815)		27,344
Change in fair value of derivatives									(187)	[1]	(5,286)	[1]	(6,096)	[1]
Amortization of interest rate lock agreements									1,952		1,508		767
Change in fair value of available-for-sale securities									14	[2]	24	[2]	3	[2]
Other									768	[3]	(575)	[3]	656	[3]
Other comprehensive income (loss)									1,460		(22,144)		22,674
Comprehensive income									$ 316,902		$ 275,493		$ 269,663

[1] Net of less than $0.1 million, $3.1 million and $3.8 million of tax expense for the fiscal years ended May 31, 2013, 2012 and 2011, respectively.

[2] Net of less than $0.1 million of tax benefit for each of the fiscal years ended May 31, 2013, 2012 and 2011, respectively.

[3] Net of $0.3 million of tax benefit, $0.2 million of tax expense and $0.2 million of tax benefit for the fiscal years ended May 31, 2013, 2012 and 2011, respectively.