Reportable Business Segments and International Operations, Reconciliation of Segment Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of segment assets to consolidated total assets
Segment assets excluding goodwill	$ 5,886.7	$ 5,932.9
Goodwill	4,103.2	4,042.6	$ 3,678.8
Other assets	55.0	28.4
Total assets	$ 10,044.9	$ 10,003.9