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						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income - basic and diluted	$ 669.6	$ 193.1	$ 461.1	$ 594.7	$ 551.4	$ 477.9	$ 1,323.8	$ 1,624.0
Weighted average shares outstanding - basic (in shares)	109.4			108.0			109.2	107.8
Dilutive effect of stock options (in shares)	4.8			7.1			5.5	7.0
Weighted average shares - diluted (in shares)	114.2			115.1			114.7	114.8
Net income per share - basic (in dollars per share)	$ 6.12			$ 5.50			$ 12.12	$ 15.06
Net income per share - diluted (in dollars per share)	$ 5.86			$ 5.17			$ 11.54	$ 14.14