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, 2018		Mar. 31, 2017	Dec. 31, 2017
Average recorded investment in impaired loans(1)	[1],[2]	$ 11,754		$ 9,123	$ 13,344	[3]
Interest income recognized on impaired loans, after designation as impaired		120		67	528	[3]
Real Estate Construction Portfolio Segment[Member] | Construction, 1-4 Family Residential [Member]
Average recorded investment in impaired loans(1)	[2],[3]	839		267	3,298
Interest income recognized on impaired loans, after designation as impaired	[3]	38		3	177
Consumer Real Estate Portfolio Segment [Member] | Closed End First Liens [Member]
Average recorded investment in impaired loans(1)	[2],[3]	3,387		606	781
Interest income recognized on impaired loans, after designation as impaired	[3]	10		9	57
Consumer Real Estate Portfolio Segment [Member] | Closed End Junior Liens [Member]
Average recorded investment in impaired loans(1)	[2],[3]	253		193	185
Interest income recognized on impaired loans, after designation as impaired	[3]	3		3	11
Consumer Real Estate Portfolio Segment [Member] | Investor Owned Residential Real Estate [Member]
Average recorded investment in impaired loans(1)	[2],[3]	323		73	329
Interest income recognized on impaired loans, after designation as impaired	[3]	4		1	1
Commercial Real Estate Portfolio Segment [Member] | Multifamily Real Estate [Member]
Average recorded investment in impaired loans(1)	[2],[3]	372		1,091	748
Interest income recognized on impaired loans, after designation as impaired	[3]	4			16
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate, Owner Occupied [Member]
Average recorded investment in impaired loans(1)	[2],[3]	2,648		3,945	4,047
Interest income recognized on impaired loans, after designation as impaired	[3]	50		32	200
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Average recorded investment in impaired loans(1)	[2],[3]	2,384		2,708	2,638
Interest income recognized on impaired loans, after designation as impaired	[3]			17
Commercial Non Real Estate Segment [Member] | Commercial and Industrial [Member]
Average recorded investment in impaired loans(1)	[2],[3]	939		237	1,282
Interest income recognized on impaired loans, after designation as impaired	[3]	11		2	64
Consumer Non Real Estate Portfolio Segment [Member] | Automobile Loan [Member]
Average recorded investment in impaired loans(1)	[2]	609	[3]	3	36
Interest income recognized on impaired loans, after designation as impaired			[3]	$ 0	$ 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.