Retirement Benefits Plans (Components of the Changes in Benefit Obligations and Fair Value of Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in Benefit Obligation
Current portion of retirement liabilities classified in accrued liabilities	$ 3.0	$ 3.1
Postretirement benefit plans
Change in Benefit Obligation
Benefit obligations at beginning of year	31.3	32.3
Interest cost	1.0	1.1	$ 1.3
Actuarial (gain)/loss	(0.8)	1.1
Benefits paid	(3.3)	(3.2)
Benefit obligations at end of year	28.2	31.3	32.3
Prior service (cost) benefit	$ 0.0	$ 0.0	$ 1.5