Stock-Based Compensation - Options (Details) (Stock Options [Member], USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Stock Options [Member]
Number of shares
Beginning Balance (in shares)	2.8
Granted (in shares)	0.2
Forfeited (in shares)	0
Exercised (in shares)	(0.1)
Ending balance (in shares)	2.9
Options exercisable (in shares)	2.4
Weighted average grant date fair value
Beginning balance (dollars per share)	$ 21.73
Granted (dollars per share)	$ 51.86
Forfeited (dollars per share)	$ 49.63
Exercised (dollars per share)	$ 18.85
Ending balance (dollars per share)	$ 23.95
Options exercisable (dollars per share)	$ 19.10
Ending balance weighted average remaining contractual term (in years)	5 years 10 months 27 days
Options exercisable weighted average remaining contractual term (in years)	5 years 2 months 1 day
Ending balance aggregate intrinsic value	$ 71.2
Options exercisable aggregate intrinsic value	76.3
Total intrinsic value of options exercised	$ 2.7	$ 7.5