Note 5 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Impaired Loans, Average Investment and Interest Income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Average recorded investment in impaired loans(1)	[1]	$ 5,359	[2]	$ 9,788	[2]	$ 13,344	[3]
Income recognized on impaired loans, after designation as impaired		171		250		528	[3]
Consumer Real Estate Portfolio Segment [Member] | Equity Lines [Member]
Average recorded investment in impaired loans(1)	[1],[3]	98
Income recognized on impaired loans, after designation as impaired	[3]	6
Consumer Real Estate Portfolio Segment [Member] | Closed End First Liens [Member]
Average recorded investment in impaired loans(1)	[1],[3]	225		1,202		781
Income recognized on impaired loans, after designation as impaired	[3]	11		41		57
Consumer Real Estate Portfolio Segment [Member] | Closed End Junior Liens [Member]
Average recorded investment in impaired loans(1)	[1],[3]			159		185
Income recognized on impaired loans, after designation as impaired	[3]			9		11
Consumer Real Estate Portfolio Segment [Member] | Investor Owned Residential Real Estate [Member]
Average recorded investment in impaired loans(1)	[1],[3]	439		808		329
Income recognized on impaired loans, after designation as impaired	[3]	17		23		1
Real Estate Construction Portfolio Segment[Member] | Construction, Other [Member]
Average recorded investment in impaired loans(1)	[1],[3]					3,298
Income recognized on impaired loans, after designation as impaired	[3]					177
Commercial Real Estate Portfolio Segment [Member] | Multifamily Real Estate [Member]
Average recorded investment in impaired loans(1)	[1],[3]	284		491		748
Income recognized on impaired loans, after designation as impaired	[3]	12		20		16
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate, Owner Occupied [Member]
Average recorded investment in impaired loans(1)	[1],[3]	913		3,038		4,047
Income recognized on impaired loans, after designation as impaired	[3]	41		75		200
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Average recorded investment in impaired loans(1)	[1],[3]	2,435		2,744		2,638
Income recognized on impaired loans, after designation as impaired	[3]	59		54
Commercial Non Real Estate Segment [Member] | Commercial and Industrial [Member]
Average recorded investment in impaired loans(1)	[1],[3]	962		1,326		1,282
Income recognized on impaired loans, after designation as impaired	[3]	25		27		64
Consumer Non Real Estate Portfolio Segment [Member] | Automobile Loan [Member]
Average recorded investment in impaired loans(1)	[1]	3	[3]	20		36	[3]
Income recognized on impaired loans, after designation as impaired			[3]	$ 1		$ 2	[3]

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

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

[3] Only classes with impaired loans are shown.