Net Income (Loss) Per Share (Tables)

12 Months Ended

Dec. 31, 2017

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,
	2017		2016		2015
Net income - basic	$	1,198,511	$	895,522	$	636,056
Effect of dilutive securities:
Convertible senior notes - interest expense and amortization of discount and note issuance costs	—		397		—
Net income - diluted	$	1,198,511	$	895,919	$	636,056
(Shares in thousands)
Weighted average shares - basic	106,338		104,719		103,061
Effect of dilutive securities:
Stock options	9,132		10,177		9,446
Restricted stock	484		474		477
Convertible senior notes	—		61		—
Warrants	—		936		2,246
Dilutive potential shares	9,616		11,648		12,169
Weighted average shares - diluted	115,954		116,367		115,230
Net income per share - basic	$	11.27	$	8.55	$	6.17
Net income per share - diluted	$	10.34	$	7.70	$	5.52

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 thousands)	2017	2016	2015
Stock options	9,161	8,041	1,343
Restricted stock	—	19	—
Convertible senior notes	—	—	994