Stock-Based Compensation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Recorded share-based compensation expense	$ 8.7	$ 8.9	$ 16.3	$ 16.3
Total unrecognized compensation costs related to non-vested share-based compensation.	$ 37.3		$ 37.3
Period for recognition			1 year 5 months 27 days
Exercises in period (shares)			1,208,054	725,612
Cash received from exercise of stock options			$ 20.8	$ 9.5