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Revenues (Narrative) (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Revenue from Contract with Customer [Abstract]        
Contract liability, revenue recognized $ 50.5 $ 45.0 $ 129.4 $ 113.5
Deferred revenue acquired $ 5.7   $ 5.7