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, 2022 |
Nov. 30, 2021 |
Nov. 30, 2022 |
Nov. 30, 2021 |
|
| Capitalized Contract Cost [Line Items] | ||||
| Amortization | $ 107.5 | $ 99.1 | ||
| Costs To Fulfill Contracts [Member] | ||||
| Capitalized Contract Cost [Line Items] | ||||
| Balance, beginning of period | $ 73.4 | $ 70.2 | 72.3 | 69.3 |
| Capitalization of costs | 7.6 | 6.5 | 15.1 | 13.6 |
| Amortization | (6.5) | (6.2) | (12.9) | (12.4) |
| Balance, end of period | 74.5 | 70.5 | 74.5 | 70.5 |
| Costs To Obtain Contracts [Member] | ||||
| Capitalized Contract Cost [Line Items] | ||||
| Balance, beginning of period | 560.6 | 491.9 | 550.2 | 488.2 |
| Capitalization of costs | 50.0 | 52.4 | 107.0 | 99.0 |
| Amortization | (48.0) | (43.8) | (94.6) | (86.7) |
| Balance, end of period | $ 562.6 | $ 500.5 | $ 562.6 | $ 500.5 |