Net Income Per Share

The Company's basic net income per share amounts have been computed by dividing net income by the weighted average number of shares of Common Stock and Class A Stock outstanding. Net income per share is presented on a combined basis, inclusive of Common Stock and Class A Stock outstanding, as each class of stock has equivalent economic rights. Diluted net income per share includes the potential dilutive effect of other securities as if such securities were converted or exercised during the period, when the effect is dilutive. 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

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