Stock-Based Compensation Plans (Schedule Of Stock Option Transactions) (Details) (USD $)	6 Months Ended
	Nov. 30, 2011
Stock-Based Compensation Plans [Abstract]
Shares Under Option, Outstanding at May 31, 2011	1,972,441
Shares Under Option, Granted	16,000
Shares Under Option, Exercised	(6,853)
Shares Under Option, Canceled	(49,144)
Shares Under Option, Outstanding at November 30, 2011	1,932,444
Shares Under Option, Exercisable at November 30, 2011	1,030,584
Weighted-Average Option Price, Outstanding at May 31, 2011	$ 39.58
Weighted-Average Option Price, Granted	$ 38.40
Weighted-Average Option Price, Exercised	$ 23.10
Weighted-Average Option Price, Canceled	$ 39.31
Weighted-Average Option Price, Outstanding at November 30, 2011	$ 39.63
Weighted-Average Option Price, Exercisable at November 30, 2011	$ 41.39