Stock-Based Compensation (Allocation of Share-based Compensation Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for recognition	1 year 8 months
Stock compensation expense	$ 15.1	$ 16.1	$ 19.5
Stock Option and Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	8.6	7.8	8.6
Performance-Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	2.5	4.1	6.7
Performance-Vesting Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	0.0	0.1	0.1
Performance-vesting Shares or Units Dividend Equivalents [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	0.1	0.1	0.2
Employee Stock Purchase Plan (ESPP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	0.9	0.8	0.7
Deferred Compensation Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 3.0	$ 3.2	$ 3.2