Earning Per Common Share (Calculation of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 12,327	$ 10,208	$ 34,319	$ 32,721
Less dividends and undistributed earnings allocated to participating securities	(25)	(27)	(72)	(100)
Net income applicable to common shareholders	$ 12,302	$ 10,181	$ 34,247	$ 32,621
Weighted average common shares outstanding - basic	17,090,000	16,939,000	17,060,000	16,837,000
Basic earnings per common share	$ 0.72	$ 0.60	$ 2.01	$ 1.94
Less dividends and undistributed earnings allocated to participating securities	$ (25)	$ (28)	$ (72)	$ (100)
Net income available to common shareholders	$ 12,302	$ 10,180	$ 34,247	$ 32,621
Dilutive effect of common stock equivalents	113,000	163,000	138,000	190,000
Weighted average common shares outstanding - diluted	17,203,000	17,102,000	17,198,000	17,027,000
Diluted earnings per common share	$ 0.72	$ 0.60	$ 1.99	$ 1.92
Antidilutive common stock equivalents	46,800	28,342	48,718	25,788