Summary of Option Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning Balance, Options			8.5
Granted, Options	0.0	0.0	1.1	1.1
Exercised, Options			(0.8)
Cancelled, Options			(0.1)
Ending Balance, Options	8.7		8.7
Exercisable at September 30, 2015, Options	4.9		4.9
Beginning Balance, Weighted-Average Exercise Price			$ 45.50
Granted, Weighted-Average Exercise Price			83.81
Exercised, Weighted-Average Exercise Price			30.21
Cancelled, Weighted-Average Exercise Price			62.55
Ending Balance, Weighted-Average Exercise Price	$ 51.38		51.38
Exercisable at September 30, 2015, Weighted-Average Exercise Price	$ 36.86		$ 36.86
Outstanding at September 30, 2015, Weighted-Average Remaining Contractual Term, years			6 years
Exercisable at September 30, 2015, Weighted-Average Remaining Contractual Term, years			4 years 3 months 18 days
Outstanding at September 30, 2015, Aggregate Intrinsic Value	$ 282.9		$ 282.9
Exercisable at September 30, 2015, Aggregate Intrinsic Value	$ 231.5		$ 231.5