Earning Per Common Share (Calculation of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income	$ 20,471	$ 11,901
Less dividends and undistributed earnings allocated to participating securities	(56)	(32)
Net income available to common shareholders	$ 20,415	$ 11,869
Weighted average common shares outstanding - basic	17,275,000	17,345,000
Basic earnings per common share	$ 1.18	$ 0.68
Less dividends and undistributed earnings allocated to participating securities	$ (56)	$ (32)
Net income available to common shareholders	$ 20,415	$ 11,869
Dilutive effect of common stock equivalents	156,000	96,000
Weighted average common shares outstanding - diluted	17,431,000	17,441,000
Diluted earnings per common share	$ 1.17	$ 0.68
Antidilutive common stock equivalents	149,575	152,010