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, 2018	Aug. 31, 2017	[1]
Basic earnings per share:
Net income	$ 243.6	$ 210.4	[2]
Weighted-average common shares outstanding	359.1	358.9	[2]
Basic earnings per share	$ 0.68	$ 0.59	[2]
Diluted earnings per share:
Dilutive effect of common share equivalents	2.4	2.4
Weighted-average common shares outstanding, assuming dilution	361.5	361.3	[2]
Diluted earnings per share	$ 0.67	$ 0.58	[2]
Weighted-average anti-dilutive common share equivalents	0.3	1.1

[1] Amounts have been adjusted to reflect the adoption of ASC Topic 606.

[2] Amounts have been adjusted to reflect the adoption of Accounting Standards Codification ("ASC") Topic 606, "Revenue from Contracts with Customers" ("ASC Topic 606").