Business and Basis of Presentation (Schedule of Prior Year Amounts Recast Affected by Cumulative Adjustment in Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Assets of discontinued operations			$ 244.3
Total current assets	$ 296.7		717.6
Total assets	1,509.7		1,838.3
Retained earnings	970.3		829.8	$ 803.8	$ 727.6	$ 598.2
Total shareholders' equity	367.3	$ 243.1	226.0	295.7	368.9	384.1
Total liabilities and shareholders' equity	$ 1,509.7		1,838.3
As Reported [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Assets of discontinued operations			279.5
Total current assets			752.8
Total assets			1,873.5
Retained earnings			865.0	839.0	762.8	633.4
Total shareholders' equity			261.2	$ 330.9	$ 404.1	$ 419.3
Total liabilities and shareholders' equity			$ 1,873.5