Income Taxes (Reconciliation Unrecognized Tax Benefits) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance at beginning of period	$ 13,709	$ 44,531	$ 103,099
Additions for tax positions of prior years	2,586	2,960	5,660
Additions based on tax positions related to the current year		1,843
Settlements	(1,270)		(5,048)
Change in tax regulations		(33,600)	(57,182)
Statute expirations	(1,963)	(2,025)	(1,998)
Balance at end of period	$ 13,062	$ 13,709	$ 44,531