Quarterly Condensed Statements of Income (Schedule of Quarterly Condensed Statements of Income) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	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, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Total interest and dividend income	$ 8,323	$ 8,131	$ 7,994	$ 7,475	$ 7,323	$ 7,458	$ 7,004	$ 6,566	$ 6,443	$ 6,279	$ 6,642	$ 6,421	$ 31,923	$ 28,351	$ 25,785
Net interest income after (recovery of) loan losses	6,983	7,286	7,518	6,844	6,838	7,109	6,985	6,890	6,364	6,162	6,345	6,035	28,631	27,822	24,906
Noninterest income	1,609	1,804	1,665	1,801	1,892	1,617	1,598	1,673	1,609	1,687	1,738	1,635	6,879	6,780	6,669
Noninterest expenses	6,089	7,310	6,166	5,630	5,823	5,909	5,747	5,711	5,395	5,871	5,832	5,554	25,195	23,190	22,652
Income before income taxes	2,503	1,780	3,017	3,015	2,907	2,817	2,836	2,852	2,578	1,978	2,251	2,116	10,315	11,412	8,923
Net income	$ 2,081	$ 1,860	$ 2,521	$ 2,539	$ 1,710	$ 2,007	$ 2,027	$ 2,042	$ 1,805	$ 1,430	$ 1,610	$ 1,525	$ 9,001	$ 7,786	$ 6,370
Net income per common share, basic (in US dollars per share)	$ 0.60	$ 0.54	$ 0.73	$ 0.73	$ 0.49	$ 0.58	$ 0.58	$ 0.59	$ 0.52	$ 0.40	$ 0.46	$ 0.43	$ 2.60	$ 2.24	$ 1.81
Net income per common share, diluted (in US dollars per share)	0.60	0.54	0.73	0.73	0.49	0.58	0.58	0.59	0.52	0.40	0.46	0.43	2.60	2.24	1.81
Dividends per common share (in USD per share)	$ 0.24	$ 0.24	$ 0.23	$ 0.23	$ 0.22	$ 0.22	$ 0.22	$ 0.22	$ 0.22	$ 0.20	$ 0.20	$ 0.20	$ 0.94	$ 0.88	$ 0.82