Net Income Per Share (Tables)

12 Months Ended

Dec. 31, 2018

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,
	2018		2017		2016
Net income - basic	$	2,444.4	$	1,198.5	$	895.5
Effect of dilutive securities:
Convertible senior notes - interest expense and amortization of discount and note issuance costs	—		—		0.4
Net income - diluted	$	2,444.4	$	1,198.5	$	895.9
(Shares in millions)
Weighted average shares - basic	107.9		106.3		104.7
Effect of dilutive securities:
Stock options	6.9		9.1		10.2
Restricted stock	—		0.5		0.5
Warrants	—		—		0.9
Dilutive potential shares	6.9		9.6		11.6
Weighted average shares - diluted	114.8		115.9		116.3
Net income per share - basic	$	22.65	$	11.27	$	8.55
Net income per share - diluted	$	21.29	$	10.34	$	7.70

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)	2018	2017	2016
Stock options	14.9	9.2	8.0