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,
	2017		2016		2017		2016
Earnings:
Net income (numerator for basic and diluted calculations)	$	227,591	$	198,719	$	605,293	$	511,294
Shares:
Weighted average outstanding shares (denominator for basic calculation)	64,488		64,146		64,430		64,281
Equivalent shares from outstanding stock options	1,165		669		1,174		663
Denominator for diluted calculation	65,653		64,815		65,604		64,944
Earnings per share:
Basic	$	3.53	$	3.10	$	9.39	$	7.95
Diluted	$	3.47	$	3.07	$	9.23	$	7.87

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. For the three months ended September 30, 2017, 0.1 million stock options and approximately 0.3 million performance contingent shares were excluded from the calculation. For the three months ended September 30, 2016, no stock options and approximately 0.7 million performance contingent shares were excluded from the calculation. Year-to-date amounts for equivalent shares from outstanding stock options and performance contingent shares are the weighted average of the individual quarterly amounts.