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 June 30,				Six months ended June 30,
	2018		2017		2018		2017
Earnings:
Net income (numerator for basic and diluted calculations)	$	204,374	$	232,190	$	304,604	$	377,702
Shares:
Weighted average outstanding shares (denominator for basic calculation)	64,071		64,449		64,278		64,401
Equivalent shares from outstanding stock options	1,179		1,159		1,277		1,204
Denominator for diluted calculation	65,250		65,608		65,555		65,605
Earnings per share:
Basic	$	3.19	$	3.60	$	4.74	$	5.86
Diluted	$	3.13	$	3.54	$	4.65	$	5.76

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 millions):



	Three months ended June 30,		Six months ended June 30,
	2018	2017	2018	2017
Excluded from common equivalent shares:
Stock options	0.2	0.2	0.3	0.3
Performance contingent shares	0.2	0.3	0.2	0.3