Consolidated Condensed Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Feb. 28, 2014	Nov. 30, 2013	Aug. 31, 2013	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 84,602			$ 74,705	$ 247,218	$ 229,465
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments	(5,121)			(8,173)	(3,727)	519
Change in fair value of derivatives	(102)			(36)	(291)	(187)
Amortization of interest rate lock agreements	488			488	1,464	1,464
Change in fair value of available-for-sale securities	1			1	(17)	(11)
Other comprehensive (loss) income	(4,734)	2,335	(172)	(7,720)	(2,571)	1,785
Comprehensive income	$ 79,868			$ 66,985	$ 244,647	$ 231,250