Service Revenue (Summary of Changes in Deferred Costs to Obtain and Fulfill Contracts) (Details) - USD ($) $ in Millions	12 Months Ended
May 31, 2020	May 31, 2019	May 31, 2018
Capitalized Contract Cost [Line Items]
Amortization	$ 186.1	$ 180.2	$ 174.7
Costs To Obtain A Contract [Member]
Capitalized Contract Cost [Line Items]
Beginning balance	464.3	455.0
Capitalization of costs	171.7	166.5
Amortization	(162.4)	(157.2)
Ending balance	473.6	464.3	455.0
Costs To Fulfill A Contract [Member]
Capitalized Contract Cost [Line Items]
Beginning balance	66.1	65.4
Capitalization of costs	24.9	23.7
Amortization	(23.7)	(23.0)
Ending balance	$ 67.3	$ 66.1	$ 65.4

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

+ 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

No definition available.

+ 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68051541&loc=SL49131252-203054

+ Details

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- Details

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