Stock-Based Compensation (Allocation of Share-based Compensation Costs) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 15.5	$ 8.4	$ 7.8
Stock Option and Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	5.3	4.4	3.7
Performance-Vesting Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	6.0	3.0	2.2
Performance-Vesting Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	0.9	0.2	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	0.4	0.3	0.3
Deferred Compensation Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense	$ 2.8	$ 0.4	$ 1.3