Summary of Option Activity (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning Balance, Options | shares	8.6
Granted, Options | shares	0.4
Exercised, Options | shares	(0.4)
Cancelled, Options | shares	(0.1)
Ending Balance, Options | shares	8.5
Exercisable at March 31, 2016, Options | shares	4.4
Beginning Balance, Weighted-Average Exercise Price | $ / shares	$ 51.77
Granted, Weighted-Average Exercise Price | $ / shares	83.53
Exercised, Weighted-Average Exercise Price | $ / shares	31.22
Cancelled, Weighted-Average Exercise Price | $ / shares	70.79
Ending Balance, Weighted-Average Exercise Price | $ / shares	54.08
Exercisable at March 31, 2016, Weighted-Average Exercise Price | $ / shares	$ 37.64
Outstanding at March 31, 2016, Weighted-Average Remaining Contractual Term, years	5 years 10 months 24 days
Exercisable at March 31, 2016, Weighted-Average Remaining Contractual Term, years	4 years 1 month 6 days
Outstanding at March 31, 2016, Aggregate Intrinsic Value | $	$ 323.1
Exercisable at March 31, 2016, Aggregate Intrinsic Value | $	$ 239.8