Earning Per Common Share (Calculation of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings Per Share [Abstract]
Net income	$ 11,057	$ 11,503	$ 21,992	$ 22,513
Less dividends and undistributed earnings allocated to participating securities	(22)	(34)	(47)	(73)
Net income applicable to common shareholders	$ 11,035	$ 11,469	$ 21,945	$ 22,440
Weighted average common shares outstanding - basic	17,067,000	16,811,000	17,045,000	16,785,000
Basic earnings per common share	$ 0.65	$ 0.68	$ 1.29	$ 1.34
Less dividends and undistributed earnings allocated to participating securities	$ (22)	$ (33)	$ (47)	$ (72)
Net income available to common shareholders	$ 11,035	$ 11,470	$ 21,945	$ 22,441
Dilutive effect of common stock equivalents	127,000	178,000	140,000	192,000
Weighted average common shares outstanding - diluted	17,194,000	16,989,000	17,185,000	16,977,000
Diluted earnings per common share	$ 0.64	$ 0.68	$ 1.28	$ 1.32
Antidilutive common stock equivalents	69,025	27,169	70,132	75,913