11. Earnings Per Common 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				Nine Months Ended
	September 30,				September 30,
(in thousands, except per share data)	2018		2017		2018		2017
Numerator:
Net income to common shareholders	$	83,878	$	58,902	$	227,530	$	160,183
Net income allocated to participating securities - basic and diluted		1,544		1,244		4,238		3,566
Net income allocated to common shareholders - basic and diluted	$	82,334	$	57,658	$	223,292	$	156,617
Denominator:
Weighted-average common shares - basic	$	85,348	$	84,749	$	85,298	$	84,577
Dilutive potential common shares		191		231		184		241
Weighted-average common shares - diluted	$	85,539	$	84,980	$	85,482	$	84,818
Earnings per common share:
Basic	$	0.96	$	0.68	$	2.62	$	1.85
Diluted	$	0.96	$	0.68	$	2.61	$	1.85

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 14,904 and 18,257, respectively, for the three and nine months ended September 30, 2018. Weighted average antidilutive potential common shares totaled 1,380 and 11,057, respectively, for the three and nine months ended September 30, 2017.