Net Income Per Share (Tables)

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Basic and diluted net income (loss) per share

The calculations of basic and diluted net income per share are as follows:

	Year Ended December 31,
	2020		2019		2018
Net income - basic and diluted	$	3,513.2	$	2,115.8	$	2,444.4
(Shares in millions)
Weighted average shares - basic	107.6		109.2		107.9
Effect of dilutive securities:
Stock options	7.0		5.4		6.9
Restricted stock	0.5		—		—
Weighted average shares - diluted	115.1		114.6		114.8
Net income per share - basic	$	32.65	$	19.38	$	22.65
Net income per share - diluted	$	30.52	$	18.46	$	21.29

Antidilutive securities

Shares which have been excluded from diluted per share amounts because their effect would have been antidilutive, include the following:

	Year Ended December 31,
(Shares in millions)	2020	2019	2018
Stock options	2.7	18.4	14.9