Summary of Option Activity (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning Balance, Options | shares	14.7
Exercised, Options | shares	(0.7)
Ending Balance, Options | shares	14.0
Exercisable at March 31, 2019, Options | shares	8.9
Beginning Balance, Weighted-Average Exercise Price | $ / shares	$ 37.63
Exercised, Weighted-Average Exercise Price | $ / shares	28.49
Ending Balance, Weighted-Average Exercise Price | $ / shares	38.00
Exercisable at March 31, 2019, Weighted-Average Exercise Price | $ / shares	$ 30.90
Outstanding at March 31, 2019, Weighted-Average Remaining Contractual Term, years	5 years 4 months 24 days
Exercisable at March 31, 2019, Weighted-Average Remaining Contractual Term, years	4 years 1 month 6 days
Outstanding at March 31, 2019, Aggregate Intrinsic Value | $	$ 465.4
Exercisable at March 31, 2019, Aggregate Intrinsic Value | $	$ 357.6