Net Income Per Share - Schedule of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income - basic and diluted	$ 624.6	$ 461.1
Weighted average shares outstanding - basic (in shares)	109.8	108.9
Weighted average shares - diluted (in shares)	115.1	115.5
Net income per share - basic (in dollars per share)	$ 5.69	$ 4.23
Net income per share - diluted (in dollars per share)	$ 5.43	$ 3.99
Stock options
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities (in shares)	5.0	6.5
Restricted stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities (in shares)	0.3	0.1