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Revenues (Narrative) (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Revenue from Contract with Customer [Abstract]        
Contract liability, revenue recognized $ 31.8 $ 29.0 $ 161.2 $ 142.5
Deferred revenue acquired $ 7.2   $ 7.2