FAIR VALUE MEASUREMENT AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Balance sheet grouping (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Financial assets:
Available-for-sale, allowance for credit losses	$ 498		$ 498	$ 90		$ 90
Loans, allowance for credit losses	1,794	$ 1,751	1,804	$ 1,970	$ 2,052	$ 2,045
Level 1 | Carrying Amount
Financial assets:
Cash and cash equivalents	14,294		6,788
Accrued interest receivable	1,569		1,247
Financial liabilities:
Deposits	238,128		210,571
Accrued interest payable	153		146
Advances from borrowers for taxes and insurance	1,200		2,349
Level 1 | Fair Value
Financial assets:
Cash and cash equivalents	14,294		6,788
Accrued interest receivable	1,569		1,247
Financial liabilities:
Deposits	237,818		187,395
Accrued interest payable	153		146
Advances from borrowers for taxes and insurance	1,200		2,349
Level 2 | Carrying Amount
Financial assets:
Securities available-for-sale, net of allowance for credit losses of $498 and $498	57,034		46,484
Federal Home Loan Bank of New York stock, at cost	3,529		3,361
Financial liabilities:
Federal Home Loan Bank advances	40,567		41,253
Level 2 | Fair Value
Financial assets:
Securities available-for-sale, net of allowance for credit losses of $498 and $498	57,034		46,484
Federal Home Loan Bank of New York stock, at cost	3,529		3,361
Financial liabilities:
Federal Home Loan Bank advances	40,567		41,253
Level 3 | Carrying Amount
Financial assets:
Loans, net of allowance for credit losses of $1,794 and $1,804	214,809		202,429
Level 3 | Fair Value
Financial assets:
Loans, net of allowance for credit losses of $1,794 and $1,804	$ 214,790		$ 189,034