Service Revenue (Summary of Changes in Deferred Revenue Related to Material Rights Performance Obligations) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2022	Nov. 30, 2021	Nov. 30, 2022	Nov. 30, 2021
Revenue from Contract with Customer [Abstract]
Balance, beginning of period	$ 52.2	$ 41.5	$ 48.9	$ 40.2
Deferral of revenue	10.0	8.7	20.1	16.3
Recognition of unearned revenue	(7.0)	(6.4)	(13.8)	(12.7)
Balance, end of period	$ 55.2	$ 43.8	$ 55.2	$ 43.8