Note 1 - Organization and Summary of Significant Accounting Policies - Accounting Standards Update and Change in Accounting Principle (Details) - USD ($)	Jan. 01, 2023	Jun. 30, 2023		Mar. 31, 2023	Dec. 31, 2022		Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Allowance for loan losses	$ 14,000,000	$ 15,560,000	[1]		$ 14,000,000	[1]
Allowance for credit losses on unfunded loan commitments	0
Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Allowance for loan losses	14,700,000
Allowance for credit losses on unfunded loan commitments	1,500,000
Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses	700,000
Allowance for credit losses on unfunded loan commitments	1,500,000
Total	2,200
Residential Portfolio Segment [Member]
Allowance for loan losses	1,472,000	1,786,000		$ 1,580,000	1,472,000		$ 1,643,000	$ 1,616,000	$ 1,596,000
Residential Portfolio Segment [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses					21,000
Residential Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Allowance for loan losses	1,493,000
Residential Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses	21,000
Commercial Real Estate Portfolio Segment [Member]
Allowance for loan losses	9,037,000	10,011,000		9,732,000	9,037,000		8,337,000	7,659,000	7,470,000
Commercial Real Estate Portfolio Segment [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses					534,000
Commercial Real Estate Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Allowance for loan losses	9,571,000
Commercial Real Estate Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses	534,000
Home Equity Portfolio Segment [Member]
Allowance for loan losses	509,000	526,000		513,000	509,000		507,000	536,000	533,000
Home Equity Portfolio Segment [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses					3,000
Home Equity Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Allowance for loan losses	512,000
Home Equity Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses	3,000
Consumer Portfolio Segment [Member]
Allowance for loan losses	342,000	318,000		344,000	342,000		361,000	357,000	365,000
Consumer Portfolio Segment [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses					1,000
Consumer Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Allowance for loan losses	343,000
Consumer Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses	1,000
Commercial Portfolio Segment [Member]
Allowance for loan losses	2,640,000	$ 2,919,000		$ 2,831,000	2,640,000		$ 2,477,000	$ 2,532,000	$ 2,536,000
Commercial Portfolio Segment [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses					$ 141,000
Commercial Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjusted Balance [Member]
Allowance for loan losses	2,781,000
Commercial Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Allowance for loan losses	$ 141,000

[1] Allowance for credit losses for the quarter ended June 30, 2023; allowance for loan losses for prior periods.