Reportable Business Segments and International Operations, Reconciliation of Segment Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation of segment assets to consolidated total assets
Segment assets excluding goodwill	$ 6,887.0	$ 5,875.6
Goodwill	5,032.1	4,867.1	$ 4,103.2
Other assets	408.2	72.8
Total assets	$ 12,327.3	$ 10,815.5