Earnings Per Share

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Earnings Per Share

10.  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 unvested stock 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)	2017		2016		2017		2016
Numerator:
Net income to common shareholders	$	58,902	$	46,719	$	160,183	$	97,465
Net income allocated to participating securities - basic and diluted		1,244		1,101		3,566		2,334
Net income allocated to common shareholders - basic and diluted	$	57,658	$	45,618	$	156,617	$	95,131
Denominator:
Weighted-average common shares - basic	$	84,749	$	77,550	$	84,577	$	77,525
Dilutive potential common shares		231		127		241		128
Weighted-average common shares - diluted	$	84,980	$	77,677	$	84,818	$	77,653
Earnings per common share:
Basic	$	0.68	$	0.59	$	1.85	$	1.23
Diluted	$	0.68	$	0.59	$	1.85	$	1.23

Potential common shares consist of employee and director stock options.  These potential common shares do not enter into the calculation of diluted earnings per share if the impact would be anti-dilutive, i.e., increase earnings per share or reduce a loss per share.  Weighted average anti-dilutive potential common shares totaled 1,380 and 11,057, respectively, for the three and nine months ended September 30, 2017.  Weighted-average anti-dilutive potential common shares totaled 317,893 and 578,863, respectively, for the three and nine months ended September 30, 2016.