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, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Earnings Per Share [Abstract]
Net income	$ 8,713	$ 7,565	$ 17,151	$ 14,365
Dividends and undistributed earnings allocated to participating securities	(40)	(30)	(74)	(57)
Net income applicable to common shareholders	$ 8,673	$ 7,535	$ 17,077	$ 14,308
Weighted average common shares outstanding - basic	16,358	16,252	16,344	16,225
Dilutive effect of common stock equivalents	34	32	37	32
Weighted average common shares outstanding - diluted	16,392	16,284	16,381	16,257
Basic earnings per common share	$ 0.53	$ 0.46	$ 1.04	$ 0.88
Diluted earnings per common share	$ 0.53	$ 0.46	$ 1.04	$ 0.88
Antidilutive common stock equivalents	394	349	393	374