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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 9,960	$ 8,900	$ 26,364	$ 26,051
Dividends and undistributed earnings allocated to participating securities	(37)	(42)	(115)	(116)
Net income applicable to common shareholders	$ 9,923	$ 8,858	$ 26,249	$ 25,935
Weighted average common shares outstanding - basic	16,563	16,366	16,473	16,351
Dilutive effect of common stock equivalents	133	48	127	41
Weighted average common shares outstanding - diluted	16,696	16,414	16,600	16,392
Basic earnings per common share	$ 0.60	$ 0.54	$ 1.59	$ 1.59
Diluted earnings per common share	$ 0.59	$ 0.54	$ 1.58	$ 1.58
Antidilutive common stock equivalents	0	400	7	342