Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Data [Line Items]
Interest and dividend income	$ 6,914	$ 6,786	$ 6,688	$ 6,448	$ 6,378	$ 6,373	$ 6,276	$ 6,117	$ 6,298	$ 6,258	$ 6,184	$ 6,112	$ 26,836	$ 25,144	$ 24,852
Interest expense	558	471	519	513	478	461	521	565	521	528	529	577	2,061	2,025	2,155
Net interest income	6,356	6,315	6,169	5,935	5,900	5,912	5,755	5,552	5,777	5,730	5,655	5,535	24,775	23,119	22,697
Provision for loan losses	0	0	75	75	150	150	150	100	45	150	75	75	150	550	345
Noninterest income	2,553	2,804	2,597	2,186	2,398	2,533	2,526	2,335	2,121	2,709	2,126	1,953	10,140	9,792	8,909
Noninterest expenses	6,295	6,179	5,926	5,821	5,684	5,674	5,556	5,390	5,577	5,552	5,286	5,179	24,221	22,304	21,594
Net income	$ 2,345	$ 2,268	$ 2,139	$ 1,759	$ 1,927	$ 2,050	$ 2,017	$ 1,884	$ 1,885	$ 2,126	$ 1,919	$ 1,764	$ 8,511	$ 7,878	$ 7,694
Earnings per common share	$ 0.53	$ 0.51	$ 0.48	$ 0.39	$ 0.44	$ 0.45	$ 0.46	$ 0.42	$ 0.43	$ 0.47	$ 0.43	$ 0.40	$ 1.91	$ 1.77	$ 1.73