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Loans and Allowance for Credit Losses on Loans - Schedule of Accounts, Notes, Loans and Financing Receivable (Detail) - USD ($) $ in Thousands	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Total loans	$ 433,544		$ 438,967
Allowance for credit losses on loans	(3,517)	$ (3,517)	(3,486)	$ (3,445)	$ (3,451)	$ (3,390)
Net loans	430,027		435,481
CRE [Member]
Total loans	87,207		86,020
Allowance for credit losses on loans	(663)	(654)	(710)	(720)	(745)	(830)
MF [Member]
Total loans	4,701		5,752
Allowance for credit losses on loans	(47)	(57)	(59)	(60)	(107)	(76)
C+I [Member]
Total loans	24,682		23,711
Allowance for credit losses on loans	(199)	(202)	(233)	(237)	(234)	(236)
ADL [Member]
Total loans	12,054		14,946
Allowance for credit losses on loans	(90)	(92)	(87)	(78)	(70)	(105)
RES [Member]
Total loans	271,089		275,235
Allowance for credit losses on loans	(1,528)	(1,560)	(1,612)	(1,652)	(1,608)	(1,601)
HELOC [Member]
Total loans	21,448		20,908
Allowance for credit losses on loans	(238)	(237)	(214)	(174)	(171)	(156)
CON [Member]
Total loans	12,363		12,395
Allowance for credit losses on loans	$ (518)	$ (542)	$ (439)	$ (477)	$ (442)	$ (357)

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