Revenues - Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Nov. 30, 2020	Aug. 31, 2020	Nov. 30, 2019	Nov. 30, 2020	Nov. 30, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Accounts Receivable, Allowance for Credit Loss, Beginning Balance	$ 20.9	$ 19.9		$ 19.9
Provision for losses on accounts receivable	2.1	1.4	$ 2.7	3.5	$ 4.3
Write-offs and other	(1.8)	(0.4)
Accounts Receivable, Allowance for Credit Loss, Ending Balance	$ 21.2	$ 20.9		$ 21.2