Service Revenue (Summary of Changes in Deferred Costs to Obtain and Fulfill Contracts) (Details) - USD ($) $ in Millions  | 
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Feb. 29, 2024  | 
Feb. 28, 2023  | 
Feb. 29, 2024  | 
Feb. 28, 2023  | 
|
| Capitalized Contract Cost [Line Items] | ||||
| Amortization | $ 173.4 | $ 163.0 | ||
| Costs To Fulfill Contracts [Member] | ||||
| Capitalized Contract Cost [Line Items] | ||||
| Balance, beginning of period | $ 75.8 | $ 74.5 | 75.3 | 72.3 | 
| Capitalization of costs | 7.5 | 8.3 | 21.2 | 23.4 | 
| Amortization | (6.7) | (6.6) | (19.9) | (19.5) | 
| Balance, end of period | 76.6 | 76.2 | 76.6 | 76.2 | 
| Costs To Obtain Contracts [Member] | ||||
| Capitalized Contract Cost [Line Items] | ||||
| Balance, beginning of period | 605.0 | 562.6 | 597.5 | 550.2 | 
| Capitalization of costs | 53.7 | 65.2 | 163.1 | 172.2 | 
| Amortization | (51.6) | (48.9) | (153.5) | (143.5) | 
| Balance, end of period | $ 607.1 | $ 578.9 | $ 607.1 | $ 578.9 | 
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- Definition 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. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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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. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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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. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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