Earning Per Common Share (Calculation of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income	$ 17,460	$ 21,040	$ 37,931	$ 32,941
Less dividends and undistributed earnings allocated to participating securities	(52)	(40)	(108)	(72)
Net income available to common shareholders	$ 17,408	$ 21,000	$ 37,823	$ 32,869
Weighted average common shares outstanding - basic	17,314,000	17,257,000	17,295,000	17,301,000
Basic earnings per common share	$ 1.01	$ 1.22	$ 2.19	$ 1.90
Less dividends and undistributed earnings allocated to participating securities	$ (52)	$ (40)	$ (108)	$ (72)
Net income available to common shareholders	$ 17,408	$ 21,000	$ 37,823	$ 32,869
Dilutive effect of common stock equivalents	122,000	35,000	150,000	76,000
Weighted average common shares outstanding - diluted	17,436,000	17,292,000	17,445,000	17,377,000
Diluted earnings per common share	$ 1.00	$ 1.21	$ 2.17	$ 1.89
Antidilutive common stock equivalents	87,924	256,721	149,650	220,305