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:



	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Net income - basic and diluted	$	551,412	$	387,744	$	1,029,392	$	636,675

(Shares in thousands)
Weighted average shares - basic	107,800		106,034		107,724		105,804
Effect of dilutive securities:
Stock options	6,664		9,602		6,959		9,310
Restricted stock	13		501		14		493
Dilutive potential shares	6,677		10,103		6,973		9,803
Weighted average shares - diluted	114,477		116,137		114,697		115,607

Net income per share - basic	$	5.12	$	3.66	$	9.56	$	6.02
Net income per share - diluted	$	4.82	$	3.34	$	8.97	$	5.51

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



	Three Months Ended June 30,		Six Months Ended June 30,
(Shares in thousands)	2018	2017	2018	2017
Stock options	14,865	7,959	14,872	11,055
Restricted stock	60	—	57	16