Service Revenue (Summary of Changes in Deferred Costs to Obtain and Fulfill Contracts) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Nov. 30, 2023	Nov. 30, 2022	Nov. 30, 2023	Nov. 30, 2022
Capitalized Contract Cost [Line Items]
Amortization			$ 115.1	$ 107.5
Costs To Fulfill Contracts [Member]
Capitalized Contract Cost [Line Items]
Balance, beginning of period	$ 75.2	$ 73.4	75.3	72.3
Capitalization of costs	7.2	7.6	13.7	15.1
Amortization	(6.6)	(6.5)	(13.2)	(12.9)
Balance, end of period	75.8	74.5	75.8	74.5
Costs To Obtain Contracts [Member]
Capitalized Contract Cost [Line Items]
Balance, beginning of period	602.6	560.6	597.5	550.2
Capitalization of costs	53.7	50.0	109.4	107.0
Amortization	(51.3)	(48.0)	(101.9)	(94.6)
Balance, end of period	$ 605.0	$ 562.6	$ 605.0	$ 562.6

Capitalized Contract Cost

No definition available.

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- Definition

Amount of amortization expense for asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 340
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479483/340-40-50-3

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 340
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479483/340-40-50-3

+ Details

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- Definition

Amount, after accumulated amortization and accumulated impairment loss, of asset recognized from cost incurred to obtain or fulfill contract with customer.

+ References

+ Details

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- Details

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