Note 5 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Restructurings By Class (Details) $ in Thousands		12 Months Ended
		Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Number of contracts		1	13	10
Pre-modification outstanding principal balance		$ 100	$ 4,213	$ 1,387
Post-modification outstanding principal balance	[1]	$ 100	$ 4,213	$ 1,387
Consumer Real Estate Portfolio Segment [Member] | Equity Lines [Member]
Number of contracts		1
Pre-modification outstanding principal balance		$ 100
Post-modification outstanding principal balance		$ 100
Consumer Real Estate Portfolio Segment [Member] | Closed End First Liens [Member]
Number of contracts			1	1
Pre-modification outstanding principal balance			$ 22	$ 8
Post-modification outstanding principal balance	[1]		$ 22	$ 8
Consumer Real Estate Portfolio Segment [Member] | Investor Owned Residential Real Estate [Member]
Number of contracts			8
Pre-modification outstanding principal balance			$ 594
Post-modification outstanding principal balance	[1]		$ 594
Real Estate Construction Portfolio Segment[Member] | Construction Loans [Member]
Number of contracts			2
Pre-modification outstanding principal balance			$ 2,882
Post-modification outstanding principal balance	[1]		$ 2,882
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate, Owner Occupied [Member]
Number of contracts			2
Pre-modification outstanding principal balance			$ 715
Post-modification outstanding principal balance	[1]		$ 715
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Number of contracts				1
Pre-modification outstanding principal balance				$ 132
Post-modification outstanding principal balance	[1]			$ 132
Commercial Non Real Estate Segment [Member]
Number of contracts				4
Commercial Non Real Estate Segment [Member] | Commercial and Industrial [Member]
Number of contracts				4
Pre-modification outstanding principal balance				$ 1,221
Post-modification outstanding principal balance	[1]			$ 1,221
Commercial Non Real Estate Segment [Member] | Automobile Loan [Member]
Number of contracts				4
Consumer Non Real Estate Portfolio Segment [Member] | Automobile Loan [Member]
Number of contracts				4
Pre-modification outstanding principal balance				$ 26
Post-modification outstanding principal balance	[1]			$ 26

[1] Post-modification outstanding recorded investment considers amounts immediately following the modification. Amounts do not reflect balances at the end of the period.