Earnings Per Share

The following table sets forth the computation of basic and diluted earnings per share on net income (in thousands, except per share information):



	Three months ended September 30,				Nine months ended September 30,
	2018		2017		2018		2017
Earnings:
Net income (numerator for basic and diluted calculations)	$	301,199	$	227,591	$	605,803	$	605,293
Shares:
Weighted average outstanding shares (denominator for basic calculation)	63,279		64,488		63,941		64,430
Equivalent shares from outstanding stock options	1,017		1,165		1,189		1,174
Denominator for diluted calculation	64,296		65,653		65,130		65,604
Earnings per share:
Basic	$	4.76	$	3.53	$	9.47	$	9.39
Diluted	$	4.68	$	3.47	$	9.30	$	9.23

The calculation of common equivalent shares does not include the impact of options having a strike or conversion price that exceeds the average stock price for the earnings period, as the result would be antidilutive. The calculation of common equivalent shares also excludes the impact of outstanding performance contingent shares, as the conditions necessary for their issuance have not been satisfied as of the end of the reporting period. The following table presents approximate amounts of stock options and performance contingent shares excluded from the calculation of common equivalent shares (in thousands):



	Three months ended September 30,		Nine months ended September 30,
	2018	2017	2018	2017
Excluded from common equivalent shares:
Stock options	227	87	349	296
Performance contingent shares	276	307	256	293