Basic and Diluted Earnings per Share

Diluted earnings attributable to shareholders per share is computed using the weighted average number of common shares and dilutive potential common shares outstanding. Dilutive potential shares represent outstanding stock options, including purchase options under the Company's employee stock purchase plan and unvested restricted stock units. Basic earnings attributable to shareholders per share is calculated using the weighted average number of common shares outstanding without taking into consideration dilutive potential common shares outstanding.

The following table reconciles the numerator and the denominator of the basic and diluted per share computations for earnings attributable to shareholders:



	Three months ended
	March 31,
(Amounts in thousands, except per share amounts)	Net earnings attributable to shareholders		Weighted average shares	Earnings per share
2018
Basic earnings attributable to shareholders	$	135,692	175,900	$	0.77
Effect of dilutive potential common shares	—		3,516	—
Diluted earnings attributable to shareholders	$	135,692	179,416	$	0.76
2017
Basic earnings attributable to shareholders	$	93,264	180,062	$	0.52
Effect of dilutive potential common shares	—		2,032	—
Diluted earnings attributable to shareholders	$	93,264	182,094	$	0.51

The following potential common shares have been excluded from the computation of diluted earnings per share because the effect would have been antidilutive:



	Three months ended
	March 31,
	2018	2017
Shares	—	3,751