Summary of Option Activity (Details) $ / shares in Units, shares in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Beginning Balance, Options | shares	14.7
Granted, Options | shares	1.4
Exercised, Options | shares	(1.5)
Cancelled, Options | shares	(0.1)
Ending Balance, Options | shares	14.5
Exercisable at June 30, 2019, Options | shares	9.1
Beginning Balance, Weighted-Average Exercise Price | $ / shares	$ 37.63
Granted, Weighted-Average Exercise Price | $ / shares	77.30
Exercised, Weighted-Average Exercise Price | $ / shares	24.41
Cancelled, Weighted-Average Exercise Price | $ / shares	50.11
Ending Balance, Weighted-Average Exercise Price | $ / shares	42.85
Exercisable at June 30, 2019 Weighted-Average Exercise Price | $ / shares	$ 34.07
Outstanding at June 30, 2019, Weighted-Average Remaining Contractual Term, years	5 years 10 months 24 days
Exercisable at June 30, 2019, Weighted-Average Remaining Contractual Term, years	4 years 2 months 12 days
Outstanding at June 30, 2019, Aggregate Intrinsic Value | $	$ 444.4
Exercisable at June 30, 2019, Aggregate Intrinsic Value | $	$ 353.6