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, 2024	Nov. 30, 2023	Nov. 30, 2024	Nov. 30, 2023
Capitalized Contract Cost [Line Items]
Amortization			$ 117.3	$ 115.1
Costs To Fulfill Contracts [Member]
Capitalized Contract Cost [Line Items]
Balance, beginning of period	$ 76.2	$ 75.2	76.6	75.3
Capitalization of costs	6.3	7.2	12.6	13.7
Amortization	(6.7)	(6.6)	(13.4)	(13.2)
Balance, end of period	75.8	75.8	75.8	75.8
Costs To Obtain Contracts [Member]
Capitalized Contract Cost [Line Items]
Balance, beginning of period	602.9	602.6	609.4	597.5
Capitalization of costs	49.9	53.7	95.2	109.4
Amortization	(52.1)	(51.3)	(103.9)	(101.9)
Balance, end of period	$ 600.7	$ 605.0	$ 600.7	$ 605.0

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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