Stock-Based Compensation Stock options granted and outstanding under either the 2005 Equity Compensation Plan or under previously adopted plans (Details) (USD $)	12 Months Ended
	May 31, 2012	May 31, 2011	May 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	7,664,703	6,467,206	6,359,424
Outstanding, begining of period, Weighted Average Exercise Price (in dollars per share)	$ 36.12	$ 37.63	$ 38.91
Granted (in shares)	1,638,907	2,030,764	1,070,798
Granted, Weighted Average Exercise Price (in dollars per share)	$ 36.26	$ 32.42	$ 28.52
Canceled (in shares)	(1,591,480)	(833,267)	(963,016)
Canceled, Weighted Average Exercise Price (in dollars per share)	$ 36.90	$ 38.76	$ 35.98
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Disclosure	103,013
Exercised (in shares)		0	0
Exercised, Weighted Average Exercise Price (in dollars per share)	$ 32.66	$ 0.00	$ 0.00
Outstanding, end of period (in shares)	7,609,117	7,664,703	6,467,206
Outstanding, end of period, Weighted Average Exercise Price (in dollars per share)	$ 36.04	$ 36.12	$ 37.63