Note 4 - Loans Receivable - Allowance for Loan Losses and Loans Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Loan balances, individually evaluated for impairment	$ 20,969	$ 22,049
Loan balances, collectively evaluated for impairment	995,260	1,037,057
Loans receivable	1,016,229	1,059,106
Allowance for loans individually evaluated	0	0
Allowance for loans collectively evaluated	8,249	8,345
Allowance for loan losses	8,249	8,345	$ 10,032	$ 8,129	$ 8,345
Real Estate Portfolio [Member] \| One-to-Four Family Residential Real Estate [Member]
Loan balances, individually evaluated for impairment	61	67
Loan balances, collectively evaluated for impairment	18,186	18,878
Loans receivable	18,247	18,945
Allowance for loans individually evaluated	0	0
Allowance for loans collectively evaluated	331	295
Allowance for loan losses	331	295	354	281	295
Real Estate Portfolio [Member] \| Multi-family Mortgage [Member]
Loan balances, individually evaluated for impairment	0	0
Loan balances, collectively evaluated for impairment	526,087	527,460
Loans receivable	526,087	527,460
Allowance for loans individually evaluated	0	0
Allowance for loans collectively evaluated	4,819	4,549
Allowance for loan losses	4,819	4,549	4,714	4,017	4,549
Real Estate Portfolio [Member] \| Nonresidential Real Estate [Member]
Loan balances, individually evaluated for impairment	0	0
Loan balances, collectively evaluated for impairment	110,319	118,016
Loans receivable	110,319	118,016
Allowance for loans individually evaluated	0	0
Allowance for loans collectively evaluated	1,444	1,166
Allowance for loan losses	1,444	1,166	1,347	1,234	1,166
Commercial Portfolio Segment [Member]
Loan balances, individually evaluated for impairment	20,908	21,982
Loan balances, collectively evaluated for impairment	339,420	371,339
Loans receivable	360,328	393,321
Allowance for loans individually evaluated	0	0
Allowance for loans collectively evaluated	1,621	2,303
Allowance for loan losses	1,621	2,303	3,576	2,548	2,303
Consumer Portfolio Segment [Member]
Loan balances, individually evaluated for impairment	0	0
Loan balances, collectively evaluated for impairment	1,248	1,364
Loans receivable	1,248	1,364
Allowance for loans individually evaluated	0	0
Allowance for loans collectively evaluated	34	32
Allowance for loan losses	$ 34	$ 32	$ 41	$ 49	$ 32

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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