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		6 Months Ended
	Nov. 30, 2020	Nov. 30, 2019	Nov. 30, 2020	Nov. 30, 2019
Basic earnings per share:
Net income	$ 272.4	$ 258.7	$ 484.0	$ 522.9
Weighted-average common shares outstanding	360.0	358.1	359.5	358.4
Basic earnings per share	$ 0.76	$ 0.72	$ 1.35	$ 1.46
Diluted earnings per share:
Net income	$ 272.4	$ 258.7	$ 484.0	$ 522.9
Weighted-average common shares outstanding	360.0	358.1	359.5	358.4
Dilutive effect of common share equivalents	2.0	2.5	2.1	2.7
Weighted-average common shares outstanding, assuming dilution	362.0	360.6	361.6	361.1
Diluted earnings per share	$ 0.75	$ 0.72	$ 1.34	$ 1.45
Weighted-average anti-dilutive common share equivalents	1.3	0.6	1.1	0.5