Summary of Significant Accounting Policies - Treasury Stock (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	May 31, 2023	May 31, 2022	May 31, 2021
Treasury stock
Repurchase of shares	$ 50.1	$ 42.4
Shares repurchased (in shares)		1.0
Restricted stock activity	8.9	$ 3.8	$ 3.2
Re-issuance of treasury stock upon exercise of stock options, net of shares withheld to satisfy statutory tax obligations	19.5	21.3	6.6
Treasury Stock
Treasury stock
Total increase (decrease) in treasury stock	(28.7)	15.0	(8.6)
Repurchase of shares	$ 50.1	42.4
Shares repurchased (in shares)	1.2
Restricted stock activity	$ 2.2	8.1	5.6
Re-issuance of treasury stock upon exercise of stock options, net of shares withheld to satisfy statutory tax obligations	$ 19.2	$ 19.3	$ 3.0