Earning Per Common Share (Calculation of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income	$ 11,901	$ 17,495
Less dividends and undistributed earnings allocated to participating securities	(32)	(34)
Net income applicable to common shareholders	$ 11,869	$ 17,461
Weighted average common shares outstanding - basic	17,345,000	17,304,000
Basic earnings per common share	$ 0.68	$ 1.01
Less dividends and undistributed earnings allocated to participating securities	$ (32)	$ (34)
Net income applicable to common shareholders	$ 11,869	$ 17,461
Dilutive effect of common stock equivalents	96,000	97,000
Weighted average common shares outstanding - diluted	17,441,000	17,401,000
Diluted earnings per common share	$ 0.68	$ 1.00
Antidilutive common stock equivalents	152,010	87,775