Earnings Per Common Share (Calculation of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 8,983	$ 8,713	$ 16,404	$ 17,151
Dividends and undistributed earnings allocated to participating securities	(39)	(40)	(78)	(74)
Net income applicable to common shareholders	$ 8,944	$ 8,673	$ 16,326	$ 17,077
Weighted average common shares outstanding - basic	16,454	16,358	16,428	16,344
Dilutive effect of common stock equivalents	127	34	130	37
Weighted average common shares outstanding - diluted	16,581	16,392	16,558	16,381
Basic earnings per common share	$ 0.54	$ 0.53	$ 0.99	$ 1.04
Diluted earnings per common share	$ 0.54	$ 0.53	$ 0.99	$ 1.04
Antidilutive common stock equivalents	241	394	394	393

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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