Stock-Based Compensation (Components of Stock-Based Compensation Expense) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]    
Stock-based compensation, equity classified awards $ 2.4 $ 3.2
Stock-based compensation, liability classified awards 0.3 (0.2)
Pre-tax compensation expense 2.7 3.0
Tax provision (1.0) (1.1)
Total stock-based compensation expense, net of tax $ 1.7 $ 1.9