Quarterly Consolidated Results of Operations (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest income	$ 19,714	$ 19,286	$ 18,774	$ 18,474	$ 18,737	$ 18,836	$ 18,732	$ 18,476	$ 76,248	$ 74,781	$ 80,943
Interest expense	1,613	1,623	1,645	1,678	1,727	1,680	1,814	1,949	6,559	7,170	11,937
Net interest income	18,101	17,663	17,129	16,796	17,010	17,156	16,918	16,527	69,689	67,611	69,006
Provision for loan losses	162	406	446	103	475	476	448	425	1,117	1,824	10,924
Net interest income after provision for loan losses	17,939	17,257	16,683	16,693	16,535	16,680	16,470	16,102	68,572	65,787	58,082
Gain on sale, call or write-down of securities	1	460	471	0	(337)	0	44	53	932	97	2,139
Noninterest income	7,341	8,896	7,146	7,326	6,808	7,289	7,804	8,909	31,641	30,778	34,374
Noninterest expense	16,969	16,771	16,357	16,661	15,926	16,045	15,674	17,199	66,758	65,052	65,780
Income before income taxes	8,312	9,842	7,943	7,358	7,080	7,924	8,644	7,865	33,455	31,513	26,676
Income taxes	1,957	2,773	2,254	2,179	1,992	2,445	2,535	2,306	9,163	9,278	8,012
Net income	$ 6,355	$ 7,069	$ 5,689	$ 5,179	$ 5,088	$ 5,479	$ 6,109	$ 5,559	$ 24,292	$ 22,235	$ 18,664
Earnings per common share:
Basic	$ 0.68	$ 0.75	$ 0.59	$ 0.53	$ 0.52	$ 0.56	$ 0.63	$ 0.57	$ 2.55	$ 2.28	$ 1.86
Diluted	$ 0.65	$ 0.71	$ 0.57	$ 0.51	$ 0.50	$ 0.54	$ 0.60	$ 0.55	$ 2.44	$ 2.19	$ 1.81
Average shares outstanding:
Basic	9,316	9,445	9,607	9,681	9,766	9,780	9,774	9,736	9,511	9,764	9,728
Diluted	9,801	9,903	10,066	10,108	10,198	10,212	10,156	10,105	464	407	270