Leases (Components of Lease Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2018
Leases [Abstract]
Fixed payment operating lease expense	$ 38.2	$ 42.9	$ 39.9
Variable payment operating lease expense	8.6
Short-term lease expense	$ 0.2