Stock-Based Compensation (Components of Stock-Based Compensation Expense) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-based compensation, equity classified awards	$ 1.8	$ 1.9	$ 6.4	$ 7.5
Stock-based compensation, liability classified awards	0.3	0.7	(0.5)	1.2
Total pre-tax stock-based compensation expense	2.1	2.6	5.9	8.7
Book income tax benefit	(0.8)	(1.0)	(2.2)	(3.3)
Total stock-based compensation expense, net of tax	$ 1.3	$ 1.6	$ 3.7	$ 5.4