Stock-Based Compensation (Components of Stock-Based Compensation Expense) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation, equity classified awards	$ 1.9	$ 1.2	$ 7.5	$ 7.1
Stock-based compensation, liability classified awards	0.7	(0.8)	1.2	(0.9)
Pre-tax compensation expense	2.6	0.4	8.7	6.2
Tax provision	(1.0)	(0.2)	(3.3)	(2.4)
Total stock-based compensation expense, net of tax	$ 1.6	$ 0.2	$ 5.4	$ 3.8