Net Income Per Share (Tables)

3 Months Ended

Mar. 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:

	Three Months Ended March 31,
	2018		2017
Net income - basic and diluted	$	477,980	$	248,931
(Shares in thousands)
Weighted average shares - basic	107,648		105,572
Effect of dilutive securities:
Stock options	7,244		9,050
Restricted stock	14		484
Dilutive potential shares	7,258		9,534
Weighted average shares - diluted	114,906		115,106
Net income per share - basic	$	4.44	$	2.36
Net income per share - diluted	$	4.16	$	2.16

Antidilutive Securities

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

	Three Months Ended March 31,
(Shares in thousands)	2018	2017
Stock options	14,878	11,535
Restricted stock	57	18