Loans and Allowance for Credit Losses on Loans - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Loans outstanding	$ 4,500,000		$ 4,500,000		$ 5,200,000
Provision (release) for credit losses	16,000	$ 120,000	(20,000)	$ 170,000
(Release) provision for credit losses on loans	20,000	30,000	80,000	65,000
Provision for credit losses for off-balance sheet	(4,000)	90,000	(100,000)	105,000
Interest income recognized on non-accrual loans	0	0	0	0
Loans past due over 90 days still accruing interest	$ 0		0		0
Non-Accrual Loans					141,000
Maximum [Member]
Reduced credit administration process for commercial relationships			$ 500,000
ASU 2016-13
Change in accounting principle, accounting standards update, adopted	true		true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2023		Jan. 01, 2023
Residential Real Estate [Member]
Loans collateralized by real estate	$ 0		$ 0		0
Real estate appraial value					216,000
RES and HELOC [Member]
Non-Accrual Loans					141,000
RES [Member]
(Release) provision for credit losses on loans	$ 44,000	$ (174,000)	$ 51,000	$ (110,000)
Non-Accrual Loans					$ 127,000