Business and Basis of Presentation (Schedule of Prior Year Amounts Recast Affected by Cumulative Adjustment in Balance Sheet) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Assets of discontinued operations	$ 276.7		$ 244.3
Total current assets	695.6		717.6
Total assets	1,890.0		1,838.3
Retained earnings	905.7	$ 859.9	829.8	$ 727.6	$ 680.3	$ 598.2
Total shareholders' equity	243.1	245.1	226.0	368.9	368.6	384.1
Total liabilities and shareholders' equity	$ 1,890.0		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		895.1	865.0	762.8	715.5	633.4
Total shareholders' equity		$ 280.3	261.2	$ 404.1	$ 403.8	$ 419.3
Total liabilities and shareholders' equity			$ 1,873.5