Quarterly Results of Operations - Summarized Unaudited Quarterly Operating Results (Detail) - 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, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Interest and dividend income	$ 9,474	$ 9,344	$ 9,115	$ 8,798	$ 8,541	$ 8,635	$ 8,419	$ 8,160	$ 36,731	$ 33,755	$ 31,727
Interest expense	2,496	2,231	1,835	1,612	1,566	1,537	1,454	1,406	8,174	5,963	5,299
Net interest income	6,978	7,113	7,280	7,186	6,975	7,098	6,965	6,754	28,557	27,792	26,428
Provision for loan losses	84	74	62	68	56	71	59	291	288	477	1,241
Net interest income after provision for loan losses	6,894	7,039	7,218	7,118	6,919	7,027	6,906	6,463	28,269	27,315	25,187
Noninterest income	1,816	1,893	2,364	1,744	1,868	2,030	1,836	2,296	7,817	8,030	7,935
Noninterest expense	6,724	7,512	7,574	7,540	7,806	7,168	7,233	7,689	29,350	29,896	29,856
Income before income taxes	1,986	1,420	2,008	1,322	981	1,889	1,509	1,070	6,736	5,449	3,266
Income taxes	368	180	323	196	1,159	486	368	135	1,067	2,148	362
Net income	$ 1,618	$ 1,240	$ 1,685	$ 1,126	$ (178)	$ 1,403	$ 1,141	$ 935	$ 5,669	$ 3,301	$ 2,904
Basic earnings (loss) per share	$ 0.26	$ 0.20	$ 0.28	$ 0.18	$ (0.03)	$ 0.22	$ 0.18	$ 0.15	$ 0.91	$ 0.53	$ 0.47
Diluted earnings (loss) per share	$ 0.26	$ 0.20	$ 0.28	$ 0.18	$ (0.03)	$ 0.22	$ 0.18	$ 0.15	$ 0.91	$ 0.53	$ 0.47
Weighted average shares outstanding:
Basic	6,266,585	6,211,636	6,142,680	6,188,413	6,202,635	6,236,075	6,228,994	6,218,706	6,233,176	6,221,632	6,233,860
Diluted	6,266,585	6,211,636	6,142,680	6,188,413	6,202,635	6,236,075	6,228,994	6,218,706	6,233,176	6,221,632	6,233,860