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, 2020	Aug. 31, 2019
Basic earnings per share:
Net income	$ 211.6	$ 264.2
Weighted-average common shares outstanding	359.1	358.6
Basic earnings per share	$ 0.59	$ 0.74
Diluted earnings per share:
Net income	$ 211.6	$ 264.2
Weighted-average common shares outstanding	359.1	358.6
Dilutive effect of common share equivalents	2.2	2.9
Weighted-average common shares outstanding, assuming dilution	361.3	361.5
Diluted earnings per share	$ 0.59	$ 0.73
Weighted-average anti-dilutive common share equivalents	1.0	0.3