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, 2019		Mar. 31, 2018	Dec. 31, 2018
Average recorded investment in impaired loans(1)	[1],[2]	$ 6,597		$ 11,754	$ 9,788	[3]
Interest income recognized on impaired loans, after designation as impaired		49		120	250	[3]
Closed End First Liens [Member] | Consumer Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1],[3]	710		3,387	1,202
Interest income recognized on impaired loans, after designation as impaired	[3]	9		10	41
Construction, 1-4 Family Residential [Member] | Real Estate Construction Portfolio Segment[Member]
Average recorded investment in impaired loans(1)	[1],[3]			839
Interest income recognized on impaired loans, after designation as impaired	[3]			38
Closed End Junior Liens [Member] | Consumer Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1],[3]	142		253	159
Interest income recognized on impaired loans, after designation as impaired	[3]	2		3	9
Investor Owned Residential Real Estate [Member] | Consumer Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1],[3]	570		323	808
Interest income recognized on impaired loans, after designation as impaired	[3]	9		4	23
Multifamily Real Estate [Member] | Commercial Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1],[3]	471		372	491
Interest income recognized on impaired loans, after designation as impaired	[3]	7		4	20
Commercial Real Estate, Owner Occupied [Member] | Commercial Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1],[3]	1,207		2,648	3,038
Interest income recognized on impaired loans, after designation as impaired	[3]	5		50	75
Commercial Real Estate Other [Member] | Commercial Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1],[3]	2,484		2,384	2,744
Interest income recognized on impaired loans, after designation as impaired	[3]	11			54
Commercial and Industrial [Member] | Commercial Non Real Estate Segment [Member]
Average recorded investment in impaired loans(1)	[1],[3]	1,002		939	1,326
Interest income recognized on impaired loans, after designation as impaired	[3]	6		11	27
Automobile Loan [Member] | Consumer Non Real Estate Portfolio Segment [Member]
Average recorded investment in impaired loans(1)	[1]	11	[3]	609	20
Interest income recognized on impaired loans, after designation as impaired			[3]		$ 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.