FAIR VALUE MEASUREMENT AND FAIR VALUE OF FINANCIAL INSTRUMENTS - Balance sheet grouping (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Jun. 30, 2026	Dec. 31, 2025	Sep. 30, 2025	Jun. 30, 2025	Dec. 31, 2024
Financial assets:
Available-for-sale, allowance for credit losses	$ 666		$ 518	$ 498		$ 498
Loans, allowance for credit losses	1,882	$ 1,847	1,915	$ 1,794	$ 1,751	$ 1,804
Carrying Amount
Financial assets:
Cash and cash equivalents	8,700		5,328
Securities available-for-sale, net of allowance for credit losses	36,654		48,635
Federal Home Loan Bank of New York stock, at cost	3,337		3,272
Federal Reserve Bank stock, at cost	270		131
Loans, net of allowance for credit losses	238,024		226,030
Accrued interest receivable	1,507		1,479
Financial liabilities:
Deposits	244,479		234,426
Federal Home Loan Bank advances	34,729		35,567
Accrued interest payable	121		120
Advances from borrowers for taxes and insurance	1,383		2,389
Fair Value
Financial assets:
Cash and cash equivalents	8,700		5,328
Securities available-for-sale, net of allowance for credit losses	36,654		48,635
Federal Home Loan Bank of New York stock, at cost	3,337		3,272
Federal Reserve Bank stock, at cost	270		131
Loans, net of allowance for credit losses	230,053		213,685
Accrued interest receivable	1,507		1,479
Financial liabilities:
Deposits	243,498		225,763
Federal Home Loan Bank advances	36,149		36,987
Accrued interest payable	121		120
Advances from borrowers for taxes and insurance	1,383		2,389
Level 1
Financial assets:
Cash and cash equivalents	8,700		5,328
Accrued interest receivable	1,507		1,479
Financial liabilities:
Deposits	88,746		85,684
Accrued interest payable	121		120
Advances from borrowers for taxes and insurance	1,383		2,389
Level 2
Financial assets:
Securities available-for-sale, net of allowance for credit losses	36,654		48,487
Federal Home Loan Bank of New York stock, at cost	3,337		3,272
Federal Reserve Bank stock, at cost	270		131
Financial liabilities:
Deposits	154,752		140,079
Federal Home Loan Bank advances	36,149		36,987
Level 3
Financial assets:
Securities available-for-sale, net of allowance for credit losses			148
Loans, net of allowance for credit losses	$ 230,053		$ 213,685