Note 3 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Impaired Loans, Average Investment and Interest Income (Details) - USD ($) $ in Thousands		9 Months Ended			12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019		Dec. 31, 2019
Average recorded investment in impaired loans(1)	[1]	$ 5,227	$ 6,729		$ 5,359	[2]
Interest income recognized on impaired loans, after designation as impaired		49	144		171
Investor Owned Residential Real Estate [Member] | Consumer Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1]	245	432		439	[2]
Interest income recognized on impaired loans, after designation as impaired	[1]	11	14		17
Equity Lines [Member] | Consumer Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)			97	[1]	98
Interest income recognized on impaired loans, after designation as impaired			5	[1]	6
Closed End First Liens [Member] | Consumer Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1]		990
Interest income recognized on impaired loans, after designation as impaired	[1]		10
Closed End Junior Liens [Member] | Consumer Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1]		137
Interest income recognized on impaired loans, after designation as impaired	[1]		6
Closed End Junior Liens [Member] | Consumer Real Estate Portfolio Segment [Member] | Financing Receivables 30 to 89 Days Past Due [Member]
Average recorded investment in impaired loans(1)	[3]				225
Closed End Junior Liens [Member] | Consumer Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Average recorded investment in impaired loans(1)	[3]				11
Commercial Real Estate, Owner Occupied [Member] | Commercial Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1]	858	1,174		913	[2]
Interest income recognized on impaired loans, after designation as impaired	[1]	16	39		41
Commercial Real Estate Other [Member] | Commercial Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1]	3,223	2,451		2,435	[2]
Interest income recognized on impaired loans, after designation as impaired	[1]				59
Multifamily Real Estate [Member] | Commercial Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1]		463		284	[2]
Interest income recognized on impaired loans, after designation as impaired	[1]		9		12
Commercial and Industrial [Member] | Commercial Non Real Estate Segment [Member]
Average recorded investment in impaired loans(1)	[1]	897	976		962	[2]
Interest income recognized on impaired loans, after designation as impaired	[1]	17	18		25
Automobile Loan [Member] | Consumer Non Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1]	$ 4	$ 9		$ 3	[2]

[1] Only classes with impaired loans are shown.

[2] Recorded investment is net of charge-offs and interest paid while a loan is in nonaccrual status.

[3] Only classes with past-due or nonaccrual loans are shown.