Earnings Per Common Share (Calculation of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 10,208	$ 10,538	$ 32,721	$ 29,633
Less dividends and undistributed earnings allocated to participating securities	(27)	(32)	(100)	(106)
Net income applicable to common shareholders	$ 10,181	$ 10,506	$ 32,621	$ 29,527
Weighted average common shares outstanding - basic	16,939,000	16,714,000	16,837,000	16,673,000
Basic earnings per common share	$ 0.60	$ 0.63	$ 1.94	$ 1.77
Less dividends and undistributed earnings allocated to participating securities	$ (28)	$ (32)	$ (100)	$ (106)
Net income available to common shareholders	$ 10,180	$ 10,506	$ 32,621	$ 29,527
Dilutive effect of common stock equivalents	163,000	141,000	190,000	159,000
Weighted average common shares outstanding - diluted	17,102,000	16,855,000	17,027,000	16,832,000
Diluted earnings per common share	$ 0.60	$ 0.62	$ 1.92	$ 1.75
Antidilutive common stock equivalents	28,342	52,426	25,788	53,853