Stock-Based Compensation (Stock Options Activity) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life	6 years
Weighted average remaining contractual life of options outstanding	6 years 3 months 18 days
Weighted average remaining contractual life of options exercisable	5 years 1 month 6 days
Weighted average grant date fair value of options granted	$ 10.38	$ 5.73	$ 4.01
Aggregate intrinsic value of total options outstanding	$ 127.2
Aggregate intrinsic value of total options vested	85.6
Intrinsic value of options exercised	16.0	27.3	16.9
Grant date fair value of options vested	$ 4.7	$ 4.0	$ 3.8
Granted at target level	$ 47.34	$ 29.56	$ 21.22
Stock Options Activity [Roll Forward]
Options outstanding, Beginning	4.8	5.6	5.8
Granted	0.7	0.9	1.2
Exercised	(0.7)	(1.6)	(1.4)
Forfeited	(0.2)	(0.1)	0
Options outstanding, Ending	4.6	4.8	5.6
Options exercisable	2.6	2.3	3.0
Stock Options, Weighted Average Exercise Price [Roll Forward]
Options outstanding, Beginning (in usd per share)	$ 21.99	$ 19.83	$ 17.88
Granted (in usd per share)	$ 47.59	$ 29.71	$ 21.47
Exercised (in usd per share)	$ 20.17	$ 18.97	$ 13.12
Forfeited (in usd per share)	$ 31.42	$ 23.10	$ 20.66
Options outstanding, Ending (in usd per share)	$ 25.49	$ 21.99	$ 19.83
Options exercisable (in usd per share)	$ 20.67	$ 19.51	$ 19.01
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.60%	0.90%	0.90%
Expected life	6 years	6 years	6 years
Dividend yield	0.80%	1.30%	1.70%
Stock volatility	21.90%	22.50%	23.30%