Unaudited Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Unaudited Quarterly Financial Information
Interest income	$ 18,801	$ 18,948	$ 19,114	$ 18,705	$ 18,607	$ 18,278	$ 18,182	$ 18,234	$ 75,568	$ 73,301
Interest expense	4,309	4,397	4,452	3,869	3,742	3,517	3,275	2,995	17,027	13,529
Net interest income	14,492	14,551	14,662	14,836	14,865	14,761	14,907	15,239	58,541	59,772
Provision (reversal of provision) for loan losses	(4)	111	(51)	5	100	(50)	60	9	61	119
Net interest income after provision for loan losses	14,496	14,440	14,713	14,831	14,765	14,811	14,847	15,230	58,480	59,653
Noninterest income	1,017	2,102	1,273	3,440	839	746	837	742	7,832	3,164
Noninterest expense	9,320	9,401	9,511	9,774	9,224	9,503	9,374	9,393	38,006	37,494
Income before income taxes	6,193	7,141	6,475	8,497	6,380	6,054	6,310	6,579	28,306	25,323
Income taxes	1,148	1,775	1,415	1,973	1,737	1,268	1,347	1,759	6,311	6,111
Net income	$ 5,045	$ 5,366	$ 5,060	$ 6,524	$ 4,643	$ 4,786	$ 4,963	$ 4,820	$ 21,995	$ 19,212
Basic earnings per share (in dollars per share)	$ 0.54	$ 0.58	$ 0.55	$ 0.71	$ 0.50	$ 0.52	$ 0.54	$ 0.52	$ 2.38	$ 2.07
Diluted earnings per share (in dollars per share)	0.53	0.57	0.54	0.70	0.50	0.51	0.53	0.51	2.34	2.03
Cash dividends declared per common share (in dollars per share)	$ 0.73	$ 0.22	$ 0.32	$ 0.22	$ 0.42	$ 0.22	$ 0.30	$ 0.20	$ 1.49	$ 1.14