11. Earnings Per Share

The Company calculates earnings per share using the two-class method. The two-class method allocates net income to each class of common stock and participating security according to common dividends declared and participation rights in undistributed earnings. Participating securities consist of nonvested share-based payment awards that contain nonforfeitable rights to dividends or dividend equivalents.

A summary of the information used in the computation of earnings per common share follows.



	Three Months Ended				Six Months Ended
	June 30,				June 30,
(in thousands, except per share data)	2018		2017		2018		2017
Numerator:
Net income to common shareholders	$	71,177	$	52,267	$	143,652	$	101,281
Net income allocated to participating securities - basic and diluted		1,328		1,166		2,694		2,322
Net income allocated to common shareholders - basic and diluted	$	69,849	$	51,101	$	140,958	$	98,959
Denominator:
Weighted-average common shares - basic	$	85,305	$	84,614	$	85,273	$	84,489
Dilutive potential common shares		178		253		178		266
Weighted-average common shares - diluted	$	85,483	$	84,867	$	85,451	$	84,755
Earnings per common share:
Basic	$	0.82	$	0.60	$	1.65	$	1.17
Diluted	$	0.82	$	0.60	$	1.65	$	1.17

Potential common shares consist of stock options, nonvested performance-based awards, and nonvested restricted share awards deferred under the Company’s nonqualified deferred compensation plan. These potential common shares do not enter into the calculation of diluted earnings per share if the impact would be antidilutive, i.e., increase earnings per share or reduce a loss per share. Weighted average antidilutive potential common shares totaled 1,816 and 913, respectively, for the three and six months ended June 30, 2018. Weighted average antidilutive potential common shares totaled 19,397 and 17,701, respectively, for the three and six months ended June 30, 2017.