Quarterly Financial Comparison (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																								12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		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, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest and dividend income	$ 13,573		$ 13,680		$ 13,395		$ 12,922		$ 12,584		$ 12,223		$ 11,928		$ 11,312		$ 11,208		$ 11,002		$ 10,935		$ 10,728		$ 53,570	$ 48,047	$ 43,873
Interest expense	2,800		2,672		2,462		2,248		2,111		2,079		2,033		1,919		1,860		1,918		1,902		1,665		10,182	8,142	7,345
Net interest income	10,773		11,008		10,933		10,674		10,473		10,144		9,895		9,393		9,348		9,084		9,033		9,063		43,388	39,905	36,528
Provision for loan losses	30		224		376		380		670		698		564		427		362		501		392		178		1,010	2,359	1,433
Net interest income after provision for loan losses	10,743		10,784		10,557		10,294		9,803		9,446		9,331		8,966		8,986		8,583		8,641		8,885		42,378	37,546	35,095
Noninterest income	1,000		1,157		1,052		875		891		842		777		850		909		466		962		962		4,084	3,360	3,299
Noninterest expense	7,746		7,442		7,530		7,379		7,316		7,311		7,292		7,240		7,556		7,031		6,888		6,943		30,097	29,159	28,418
Income before income taxes	3,997		4,499		4,079		3,790		3,378		2,977		2,816		2,576		2,339		2,018		2,715		2,904		16,365	11,747	9,976
Provision for income taxes	4,456		1,717		1,536		1,448		1,356		1,014		1,078		968		811		735		1,004		1,083		9,157	4,416	3,633
Net income									$ 2,022		$ 1,963		$ 1,738		$ 1,608		1,528		1,283		1,711		1,821		7,208	7,331	6,343
Preferred stock dividends																							23				23
Net income available to common shareholders	$ (459)		$ 2,782		$ 2,543		$ 2,342										$ 1,528		$ 1,283		$ 1,711		$ 1,798		$ 7,208	$ 7,331	$ 6,320
Earnings Per Common Share
Basic	$ (0.10)	[1]	$ 0.60	[1]	$ 0.55	[1]	$ 0.51	[1]	$ 0.44	[1]	$ 0.43	[1]	$ 0.38	[1]	$ 0.35	[1]	$ 0.33	[1]	$ 0.28	[1]	$ 0.37	[1]	$ 0.38	[1]	$ 1.56	$ 1.59	$ 1.36
Diluted	$ (0.10)	[1]	$ 0.60	[1]	$ 0.55	[1]	$ 0.51	[1]	$ 0.44	[1]	$ 0.42	[1]	$ 0.38	[1]	$ 0.35	[1]	$ 0.33	[1]	$ 0.27	[1]	$ 0.37	[1]	$ 0.38	[1]	$ 1.56	$ 1.59	$ 1.35
Parent Company [Member]
Interest expense																									$ 1,865	$ 1,795	$ 1,599
Net interest income																									5,699	3,724	1,227
Income before income taxes																									2,731	1,614	(194)
Provision for income taxes																									(1,583)	(1,321)	(1,009)
Net income																									7,208	7,331	6,343
Preferred stock dividends																											23
Net income available to common shareholders																									$ 7,208	$ 7,331	$ 6,320

[1] Earnings per share are based upon quarterly results and, when added, may not total the annual earnings per share amounts.