Note 3 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Impaired Loans, Average Investment and Interest Income (Details) - USD ($) $ in Thousands		3 Months Ended			12 Months Ended
		Mar. 31, 2020		Mar. 31, 2019	Dec. 31, 2019
Average recorded investment in impaired loans(1)	[1],[2],[3]	$ 5,677		$ 6,597	$ 5,359
Interest income recognized on impaired loans, after designation as impaired		26		49	171
Consumer Real Estate Portfolio Segment [Member] | Equity Lines [Member]
Average recorded investment in impaired loans(1)		100	[1],[2],[4]		98
Interest income recognized on impaired loans, after designation as impaired		2	[4]		6
Consumer Real Estate Portfolio Segment [Member] | Closed End First Liens [Member]
Average recorded investment in impaired loans(1)	[1],[2],[4]	22		710
Interest income recognized on impaired loans, after designation as impaired	[4]			9
Consumer Real Estate Portfolio Segment [Member] | Closed End Junior Liens [Member]
Average recorded investment in impaired loans(1)	[1],[2],[4]			142
Interest income recognized on impaired loans, after designation as impaired	[4]			2
Consumer Real Estate Portfolio Segment [Member] | Closed End Junior Liens [Member] | Financing Receivables 30 to 89 Days Past Due [Member]
Average recorded investment in impaired loans(1)	[1],[2]				225
Consumer Real Estate Portfolio Segment [Member] | Closed End Junior Liens [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Average recorded investment in impaired loans(1)	[1],[2]				11
Consumer Real Estate Portfolio Segment [Member] | Investor Owned Residential Real Estate [Member]
Average recorded investment in impaired loans(1)	[1],[2],[4]	487		570	439
Interest income recognized on impaired loans, after designation as impaired	[4]	4		9	17
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate, Owner Occupied [Member]
Average recorded investment in impaired loans(1)	[1],[2],[4]	890		1,207	913
Interest income recognized on impaired loans, after designation as impaired	[4]	6		5	41
Commercial Real Estate Portfolio Segment [Member] | Multifamily Real Estate [Member]
Average recorded investment in impaired loans(1)	[1],[2],[4]			471	284
Interest income recognized on impaired loans, after designation as impaired	[4]			7	12
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Average recorded investment in impaired loans(1)	[1],[2],[4]	3,257		2,484	2,435
Interest income recognized on impaired loans, after designation as impaired	[4]	8		11	59
Commercial Non Real Estate Segment [Member] | Commercial and Industrial [Member]
Average recorded investment in impaired loans(1)	[1],[2],[4]	917		1,002	962
Interest income recognized on impaired loans, after designation as impaired	[4]	6		6	25
Consumer Non Real Estate Portfolio Segment [Member] | Automobile Loan [Member]
Average recorded investment in impaired loans(1)	[1],[2]	4	[4]	11	3	[4]
Interest income recognized on impaired loans, after designation as impaired			[4]			[4]

[1] Only classes with past due or nonaccrual loans are presented

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

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

[4] Only classes with impaired loans are shown.