Basic and Diluted Earnings Per Share (Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Aug. 31, 2021	Aug. 31, 2020
Basic earnings per share:
Net income	$ 333.6	$ 211.6
Weighted-average common shares outstanding	360.1	359.1
Basic earnings per share	$ 0.93	$ 0.59
Diluted earnings per share:
Net income	$ 333.6	$ 211.6
Weighted-average common shares outstanding	360.1	359.1
Dilutive effect of common share equivalents	2.7	2.2
Weighted-average common shares outstanding, assuming dilution	362.8	361.3
Diluted earnings per share	$ 0.92	$ 0.59
Weighted-average anti-dilutive common share equivalents	0.2	1.0