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, 2021	Nov. 30, 2020	Nov. 30, 2021	Nov. 30, 2020
Basic earnings per share:
Net income	$ 332.1	$ 272.4	$ 665.7	$ 484.0
Weighted-average common shares outstanding	360.7	360.0	360.4	359.5
Basic earnings per share	$ 0.92	$ 0.76	$ 1.85	$ 1.35
Diluted earnings per share:
Net income	$ 332.1	$ 272.4	$ 665.7	$ 484.0
Weighted-average common shares outstanding	360.7	360.0	360.4	359.5
Dilutive effect of common share equivalents	2.4	2.0	2.5	2.1
Weighted-average common shares outstanding, assuming dilution	363.1	362.0	362.9	361.6
Diluted earnings per share	$ 0.91	$ 0.75	$ 1.83	$ 1.34
Weighted-average anti-dilutive common share equivalents	0.4	1.3	0.3	1.1