Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Recorded stock-based compensation expense	$ 7.4	$ 4.6
Total unrecognized compensation costs related to non-vested share-based compensation.	40.9
Weighted average period over which costs will be recognized	1 year 5 months 19 days
Common stock shares issued during period to award payment (shares)	614,851	1,687,043
Cash received from exercise of stock options and purchases	$ 8.6	$ 29.7