Service Revenue (Summary of Changes in Deferred Costs to Obtain and Fulfill Contracts) (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2022	May 31, 2021	May 31, 2020
Capitalized Contract Cost [Line Items]
Amortization	$ 202.1	$ 191.4	$ 186.1
Costs To Fulfill Contracts [Member]
Capitalized Contract Cost [Line Items]
Balance, beginning of period	69.3	67.3
Capitalization of costs	28.0	26.2
Amortization	(25.0)	(24.2)
Balance, end of period	72.3	69.3	67.3
Costs To Obtain Contracts [Member]
Capitalized Contract Cost [Line Items]
Balance, beginning of period	488.2	473.6
Capitalization of costs	239.1	181.8
Amortization	(177.1)	(167.2)
Balance, end of period	$ 550.2	$ 488.2	$ 473.6