Stock-Based Compensation - Stock Options Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average remaining contractual life of options outstanding	5 years 10 months 24 days
Weighted average remaining contractual life of options exercisable	4 years 9 months 18 days
Aggregate intrinsic value of total options outstanding	$ 481.2
Aggregate intrinsic value of total options vested	$ 351.7
Weighted average grant date fair value of options granted (in dollars per share)	$ 40.28	$ 24.72	$ 20.16
Intrinsic value of options exercised	$ 88.8	$ 46.9	$ 61.3
Grant date fair value of options vested	$ 8.4	$ 7.5	$ 8.3
Stock Options Activity [Roll Forward]
Options outstanding, beginning (in shares)	2.7	3.0	3.5
Granted (in shares)	0.2	0.3	0.5
Exercised (in shares)	(0.5)	(0.6)	(1.0)
Forfeited (in shares)	0.0	0.0	0.0
Options outstanding, ending (in shares)	2.4	2.7	3.0
Options exercisable (in shares)	1.6	1.6	1.7
Stock Options, Weighted Average Exercise Price [Roll Forward]
Options outstanding, beginning (in dollars per share)	$ 67.02	$ 58.93	$ 48.76
Granted (in dollars per share)	178.11	103.40	90.36
Exercised (in dollars per share)	49.99	46.42	35.95
Forfeited (in dollars per share)	103.51	92.71	75.32
Options outstanding, ending (in dollars per share)	81.37	67.02	58.93
Options exercisable (in dollars per share)	$ 62.42	$ 53.12	$ 45.32
Share-based Payment Arrangement, Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards, expiration period	10 years
Risk-free interest rate	1.30%	2.30%	2.70%
Stock volatility	22.40%	22.50%	19.80%
Dividend yield	0.40%	0.70%	0.70%
Expected life	5 years 8 months 12 days	5 years 8 months 12 days	5 years 8 months 12 days