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, 2019		Sep. 30, 2018	Dec. 31, 2018
Average recorded investment in impaired loans(1)	[1],[2]	$ 6,729		$ 12,684	$ 9,788	[3]
Interest income recognized on impaired loans, after designation as impaired		144		414	250	[3]
Consumer Real Estate Portfolio Segment [Member] | Equity Lines [Member]
Average recorded investment in impaired loans(1)	[1],[3]	97
Interest income recognized on impaired loans, after designation as impaired	[3]	5
Consumer Real Estate Portfolio Segment [Member] | Closed End First Liens [Member]
Average recorded investment in impaired loans(1)	[1],[3]	990		891	1,202
Interest income recognized on impaired loans, after designation as impaired	[3]	10		40	41
Consumer Real Estate Portfolio Segment [Member] | Closed End Junior Liens [Member]
Average recorded investment in impaired loans(1)	[1],[3]	137		162	159
Interest income recognized on impaired loans, after designation as impaired	[3]	6		7	9
Consumer Real Estate Portfolio Segment [Member] | Investor Owned Residential Real Estate [Member]
Average recorded investment in impaired loans(1)	[1],[3]	432		661	808
Interest income recognized on impaired loans, after designation as impaired	[3]	14		18	23
Real Estate Construction Portfolio Segment[Member] | Construction, 1-4 Family Residential [Member]
Average recorded investment in impaired loans(1)	[1],[3]			2,697
Interest income recognized on impaired loans, after designation as impaired	[3]			108
Commercial Real Estate Portfolio Segment [Member] | Multifamily Real Estate [Member]
Average recorded investment in impaired loans(1)	[1],[3]	463		298	491
Interest income recognized on impaired loans, after designation as impaired	[3]	9		12	20
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate, Owner Occupied [Member]
Average recorded investment in impaired loans(1)	[1],[3]	1,174		3,934	3,038
Interest income recognized on impaired loans, after designation as impaired	[3]	39		145	75
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Average recorded investment in impaired loans(1)	[1],[3]	2,451		2,829	2,744
Interest income recognized on impaired loans, after designation as impaired	[3]	43		55	54
Commercial Non Real Estate Segment [Member] | Commercial and Industrial [Member]
Average recorded investment in impaired loans(1)	[1],[3]	976		1,188	1,326
Interest income recognized on impaired loans, after designation as impaired	[3]	18		28	27
Consumer Non Real Estate Portfolio Segment [Member] | Automobile Loan [Member]
Average recorded investment in impaired loans(1)	[1]	9	[3]	24	20
Interest income recognized on impaired loans, after designation as impaired			[3]	$ 1	$ 1	[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.