Revenues - Allowance for Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2020	Aug. 31, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Accounts Receivable, Allowance for Credit Loss, Beginning Balance	$ 19.9
Provision for losses on accounts receivable	1.4	$ 1.6
Write-offs and other	(0.4)
Accounts Receivable, Allowance for Credit Loss, Ending Balance	$ 20.9