Service Revenue (Summary of Changes in Deferred Costs to Obtain and Fulfill Contracts) (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2023	May 31, 2022	May 31, 2021
Capitalized Contract Cost [Line Items]
Amortization	$ 219.1	$ 202.1	$ 191.4
Costs To Fulfill Contracts [Member]
Capitalized Contract Cost [Line Items]
Balance, beginning of period	72.3	69.3
Capitalization of costs	28.9	28.0
Amortization	(25.9)	(25.0)
Balance, end of period	75.3	72.3	69.3
Costs To Obtain Contracts [Member]
Capitalized Contract Cost [Line Items]
Balance, beginning of period	550.2	488.2
Capitalization of costs	240.5	239.1
Amortization	(193.2)	(177.1)
Balance, end of period	$ 597.5	$ 550.2	$ 488.2