Consolidated Condensed Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Nov. 30, 2014	Aug. 31, 2014	Nov. 30, 2013	Aug. 31, 2013	Nov. 30, 2014	Nov. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 120,412us-gaap_NetIncomeLoss		$ 84,862us-gaap_NetIncomeLoss		$ 230,520us-gaap_NetIncomeLoss	$ 162,616us-gaap_NetIncomeLoss
Other comprehensive (loss) income, net of tax:
Foreign currency translation adjustments	(9,778)		2,040		(11,893)	1,394
Change in fair value of derivatives	(21)		(189)		(4)	(189)
Amortization of interest rate lock agreements	488		488		976	976
Change in fair value of available-for-sale securities	3		(4)		3	(18)
Other comprehensive (loss) income	(9,308)	(1,610)	2,335	(172)	(10,918)	2,163
Comprehensive income	$ 111,104us-gaap_ComprehensiveIncomeNetOfTax		$ 87,197us-gaap_ComprehensiveIncomeNetOfTax		$ 219,602us-gaap_ComprehensiveIncomeNetOfTax	$ 164,779us-gaap_ComprehensiveIncomeNetOfTax

Other Comprehensive Income (Loss), Amortization of Interest Rate Lock Agreements, Net of Tax

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

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Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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