Stock-Based Compensation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock-based compensation expense
Stock-based compensation expense	$ 18.9	$ 15.8	$ 13.9
Tax benefit from stock options exercised during the period	5.3	6.8	8.5
Non-qualified stock options
Stock-based compensation expense
Stock-based compensation expense	3.8	4.5	4.1
RSUs
Stock-based compensation expense
Stock-based compensation expense	6.0	6.5	5.0
PRSUs
Stock-based compensation expense
Stock-based compensation expense	8.8	4.6	4.7
Employee stock purchase plan
Stock-based compensation expense
Stock-based compensation expense	$ 0.3	$ 0.2	$ 0.1