Net Income Per Share (Tables)

12 Months Ended

Dec. 31, 2019

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,
	2019		2018		2017
Net income - basic and diluted	$	2,115.8	$	2,444.4	$	1,198.5
(Shares in millions)
Weighted average shares - basic	109.2		107.9		106.3
Effect of dilutive securities:
Stock options	5.4		6.9		9.1
Restricted stock	—		—		0.5
Weighted average shares - diluted	114.6		114.8		115.9
Net income per share - basic	$	19.38	$	22.65	$	11.27
Net income per share - diluted	$	18.46	$	21.29	$	10.34

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)	2019	2018	2017
Stock options	18.4	14.9	9.2