Earnings Per Common Share (Calculation of Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share [Abstract]
Net income	$ 8,900	$ 7,582	$ 26,051	$ 21,947
Dividends and undistributed earnings allocated to participating securities	(42)	(27)	(116)	(84)
Net income applicable to common shareholders	$ 8,858	$ 7,555	$ 25,935	$ 21,863
Weighted average common shares outstanding - basic	16,366	16,278	16,351	16,242
Dilutive effect of common stock equivalents	48	16	41	27
Weighted average common shares outstanding - diluted	16,414	16,294	16,392	16,269
Basic earnings per common share	$ 0.54	$ 0.46	$ 1.59	$ 1.35
Diluted earnings per common share	$ 0.54	$ 0.46	$ 1.58	$ 1.34
Antidilutive common stock equivalents	400	412	342	385