Loans and Allowance for Credit Losses on Loans - Summary of Impact of Adoption (Detail) - USD ($)	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Jan. 01, 2023	Dec. 31, 2022
Assets [Abstract]
Allowance for credit losses on loans	$ 3,445,000	$ 3,451,000	$ 3,390,000	$ 3,349,000	$ 3,319,000		$ 3,581,000
Liabilities [Abstract]
Allowance for credit losses on OBS credit exposures	291,000		391,000
Stockholders' Equity [Abstract]
Retained earnings	26,492,000		25,597,000
ASU 2016-13 | As reported under ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						$ 3,286,000
Liabilities [Abstract]
Allowance for credit losses on OBS credit exposures						308,000
Stockholders' Equity [Abstract]
Retained earnings						36,253,000
ASU 2016-13 | Pre-ASC 326 Adoption [Member]
Assets [Abstract]
Allowance for credit losses on loans						3,581,000
Liabilities [Abstract]
Allowance for credit losses on OBS credit exposures						18,000
Stockholders' Equity [Abstract]
Retained earnings						36,248,000
ASU 2016-13 | Impact of adopting ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						(295,000)	(295,000)
Liabilities [Abstract]
Allowance for credit losses on OBS credit exposures						290,000
Stockholders' Equity [Abstract]
Retained earnings						5,000
CRE [Member]
Assets [Abstract]
Allowance for credit losses on loans	720,000	745,000	830,000	788,000	806,000		942,000
CRE [Member] | ASU 2016-13 | As reported under ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						788,000
CRE [Member] | ASU 2016-13 | Pre-ASC 326 Adoption [Member]
Assets [Abstract]
Allowance for credit losses on loans						942,000
CRE [Member] | ASU 2016-13 | Impact of adopting ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						(154,000)	(154,000)
MF [Member]
Assets [Abstract]
Allowance for credit losses on loans	60,000	107,000	76,000	71,000	49,000		54,000
MF [Member] | ASU 2016-13 | As reported under ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						55,000
MF [Member] | ASU 2016-13 | Pre-ASC 326 Adoption [Member]
Assets [Abstract]
Allowance for credit losses on loans						54,000
MF [Member] | ASU 2016-13 | Impact of adopting ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						1,000	1,000
C+I [Member]
Assets [Abstract]
Allowance for credit losses on loans	237,000	234,000	236,000	288,000	277,000		184,000
C+I [Member] | ASU 2016-13 | As reported under ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						273,000
C+I [Member] | ASU 2016-13 | Pre-ASC 326 Adoption [Member]
Assets [Abstract]
Allowance for credit losses on loans						184,000
C+I [Member] | ASU 2016-13 | Impact of adopting ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						89,000	89,000
ADL [Member]
Assets [Abstract]
Allowance for credit losses on loans	78,000	70,000	105,000	101,000	70,000		138,000
ADL [Member] | ASU 2016-13 | As reported under ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						120,000
ADL [Member] | ASU 2016-13 | Pre-ASC 326 Adoption [Member]
Assets [Abstract]
Allowance for credit losses on loans						138,000
ADL [Member] | ASU 2016-13 | Impact of adopting ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						(18,000)	(18,000)
RES [Member]
Assets [Abstract]
Allowance for credit losses on loans	1,652,000	1,608,000	1,601,000	1,736,000	1,910,000		2,048,000
RES [Member] | ASU 2016-13 | As reported under ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						1,847,000
RES [Member] | ASU 2016-13 | Pre-ASC 326 Adoption [Member]
Assets [Abstract]
Allowance for credit losses on loans						2,048,000
RES [Member] | ASU 2016-13 | Impact of adopting ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						(201,000)	(202,000)
HELOC [Member]
Assets [Abstract]
Allowance for credit losses on loans	174,000	171,000	156,000	161,000	85,000		81,000
HELOC [Member] | ASU 2016-13 | As reported under ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						88,000
HELOC [Member] | ASU 2016-13 | Pre-ASC 326 Adoption [Member]
Assets [Abstract]
Allowance for credit losses on loans						81,000
HELOC [Member] | ASU 2016-13 | Impact of adopting ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						7,000	7,000
CON [Member]
Assets [Abstract]
Allowance for credit losses on loans	477,000	442,000	357,000	204,000	109,000		100,000
CON [Member] | ASU 2016-13 | As reported under ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						114,000
CON [Member] | ASU 2016-13 | Pre-ASC 326 Adoption [Member]
Assets [Abstract]
Allowance for credit losses on loans						100,000
CON [Member] | ASU 2016-13 | Impact of adopting ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						14,000	14,000
Unallocated [Member]
Assets [Abstract]
Allowance for credit losses on loans	$ 47,000	$ 74,000	$ 29,000	$ 0	$ 13,000		34,000
Unallocated [Member] | ASU 2016-13 | As reported under ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						1,000
Unallocated [Member] | ASU 2016-13 | Pre-ASC 326 Adoption [Member]
Assets [Abstract]
Allowance for credit losses on loans						34,000
Unallocated [Member] | ASU 2016-13 | Impact of adopting ASC 326 [Member]
Assets [Abstract]
Allowance for credit losses on loans						$ (33,000)	$ (32,000)