Quarterly report pursuant to Section 13 or 15(d)

Service Revenue (Summary of Changes in Deferred Revenue Related to Set-Up Fees) (Details)

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Service Revenue (Summary of Changes in Deferred Revenue Related to Set-Up Fees) (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Nov. 30, 2021
Nov. 30, 2020
Nov. 30, 2021
Nov. 30, 2020
Service Revenue [Abstract]        
Balance, beginning of period $ 41.5 $ 40.2 $ 40.2 $ 42.6
Deferral of revenue 8.7 5.7 16.3 9.7
Recognition of unearned revenue (6.4) (6.3) (12.7) (12.7)
Balance, end of period $ 43.8 $ 39.6 $ 43.8 $ 39.6