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, 2019	Nov. 30, 2018	Nov. 30, 2019	Nov. 30, 2018
Basic earnings per share:
Net income	$ 258.7	$ 235.8	$ 522.9	$ 479.4	[1]
Weighted-average common shares outstanding	358.1	359.1	358.4	359.1
Basic earnings per share	$ 0.72	$ 0.66	$ 1.46	$ 1.34
Diluted earnings per share:
Net income	$ 258.7	$ 235.8	$ 522.9	$ 479.4	[1]
Weighted-average common shares outstanding	358.1	359.1	358.4	359.1
Dilutive effect of common share equivalents	2.5	2.4	2.7	2.4
Weighted-average common shares outstanding, assuming dilution	360.6	361.5	361.1	361.5
Diluted earnings per share	$ 0.72	$ 0.65	$ 1.45	$ 1.33
Weighted-average anti-dilutive common share equivalents	0.6	0.6	0.5	0.5

[1] Amounts have been adjusted to reflect adoption of Accounting Standards Update (“ASU”) No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force).”