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				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income - basic and diluted	$ 897.3	$ 624.6	$ 193.1	$ 461.1	$ 1,521.9	$ 654.2
Weighted average shares outstanding - basic (in shares)	109.6		109.2		109.7	109.1
Weighted average shares - diluted (in shares)	117.9		114.6		116.8	115.0
Net income per share - basic (in dollars per share)	$ 8.19		$ 1.77		$ 13.87	$ 6.00
Net income per share - diluted (in dollars per share)	$ 7.61		$ 1.68		$ 13.03	$ 5.69
Stock options
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities (in shares)	7.8		5.4		6.7	5.9
Restricted stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities (in shares)	0.5		0.0		0.4	0.0