Earning Per Common Share (Calculation of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 13,199	$ 11,057	$ 24,981	$ 21,992
Less dividends and undistributed earnings allocated to participating securities	(29)	(22)	(56)	(47)
Net income applicable to common shareholders	$ 13,170	$ 11,035	$ 24,925	$ 21,945
Weighted average common shares outstanding - basic	17,206,000	17,067,000	17,196,000	17,045,000
Basic earnings per common share	$ 0.77	$ 0.65	$ 1.45	$ 1.29
Less dividends and undistributed earnings allocated to participating securities	$ (29)	$ (22)	$ (56)	$ (47)
Net income available to common shareholders	$ 13,170	$ 11,035	$ 24,925	$ 21,945
Dilutive effect of common stock equivalents	110,000	127,000	116,000	140,000
Weighted average common shares outstanding - diluted	17,316,000	17,194,000	17,312,000	17,185,000
Diluted earnings per common share	$ 0.76	$ 0.64	$ 1.44	$ 1.28
Antidilutive common stock equivalents	3,475	69,025	0	70,132