Selected Quarterly Data (Unaudited) - Summary of Selected Quarterly Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2021	Sep. 30, 2020
Quarterly Financial Information Disclosure [Abstract]
Total interest income	$ 14,709	$ 14,403	$ 14,663	$ 14,912	$ 15,362	$ 15,853	$ 16,344	$ 16,513	$ 58,687	$ 64,072
Total interest expense	910	1,251	1,632	2,000	2,913	3,653	4,612	4,687	5,793	15,865
NET INTEREST INCOME	13,799	13,152	13,031	12,912	12,449	12,200	11,732	11,826	52,894	48,207
Provision for loan losses	300	600	900	900	1,100	1,300	500	375	2,700	3,275
NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES	13,499	12,552	12,131	12,012	11,349	10,900	11,232	11,451	50,194	44,932
Total noninterest income	2,550	2,293	3,515	3,135	5,241	2,883	2,705	2,426	11,493	13,255
Total noninterest expense	11,159	10,018	10,435	10,178	11,871	9,130	9,824	9,763	41,790	40,588
Income before income tax (benefit) expense	4,890	4,827	5,211	4,969	4,719	4,653	4,113	4,114
Income taxes expense	967	801	871	834	897	876	706	704	3,473	3,183
NET INCOME	$ 3,923	$ 4,026	$ 4,340	$ 4,135	$ 3,822	$ 3,777	$ 3,407	$ 3,410	$ 16,424	$ 14,416
Net income
Basic	$ 0.40	$ 0.41	$ 0.43	$ 0.41	$ 0.35	$ 0.37	$ 0.33	$ 0.33	$ 1.65	$ 1.39
Diluted	$ 0.40	$ 0.41	$ 0.43	$ 0.41	$ 0.35	$ 0.37	$ 0.33	$ 0.33	$ 1.65	$ 1.39
Average shares outstanding
Basic	9,737,685	9,905,725	10,033,012	10,071,087	10,159,246	10,260,495	10,462,013	10,482,273	9,945,528	10,347,483
Diluted	9,738,696	9,907,788	10,035,027	10,073,907	10,159,246	10,260,729	10,462,013	10,482,283	9,947,504	10,347,483