Leases (Lease Expense) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Nov. 30, 2019	Nov. 30, 2019
Leases [Abstract]
Operating lease expense	$ 7.1	$ 14.2
Finance Lease, Right-of-Use Asset, Amortization	0.5	0.9
Accretion of lease liabilities	0.1	0.2
Total lease expense	$ 7.7	$ 15.3