Revenues - Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Feb. 28, 2021	Nov. 30, 2020	Aug. 31, 2020	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Accounts Receivable, Allowance for Credit Loss, Beginning Balance	$ 21.2	$ 20.9	$ 19.9		$ 19.9
Provision for losses on accounts receivable	(0.1)	2.1	1.4	$ 3.0	3.4	$ 7.3
Write-offs and other	(2.1)	(1.8)	(0.4)
Accounts Receivable, Allowance for Credit Loss, Ending Balance	$ 19.0	$ 21.2	$ 20.9		$ 19.0