Summary of Option Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ 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 Sharebased Payments [Abstract]
Beginning Balance, Options			8.5
Granted, Options	1.1	1.1	1.1	1.1
Exercised, Options			(0.6)
Cancelled, Options			(0.1)
Ending Balance, Options	8.9		8.9
Exercisable at June 30, 2015, Options	5.1		5.1
Beginning Balance, Weighted-Average Exercise Price			$ 45.50
Granted, Weighted-Average Exercise Price			83.81
Exercised, Weighted-Average Exercise Price			27.33
Cancelled, Weighted-Average Exercise Price			61.90
Ending Balance, Weighted-Average Exercise Price	$ 51.14		51.14
Exercisable at June 30, 2015, Weighted-Average Exercise Price	$ 36.91		$ 36.91
Outstanding at June 30, 2015, Weighted-Average Remaining Contractual Term, years			6 years 3 months 18 days
Exercisable at June 30, 2015, Weighted-Average Remaining Contractual Term, years			4 years 7 months 6 days
Outstanding at June 30, 2015, Aggregate Intrinsic Value	$ 270.3		$ 270.3
Exercisable at June 30, 2015, Aggregate Intrinsic Value	$ 226.2		$ 226.2