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, 2017		Dec. 31, 2016		Dec. 31, 2015
Average recorded investment in impaired loans	[2]	$ 13,344	[1]	$ 11,585	[1]	$ 17,297
Income recognized on impaired loans, after designation as impaired		528		553		769
Real Estate Construction Portfolio Segment[Member] | Construction, Other [Member]
Average recorded investment in impaired loans	[2],[3]	3,298
Income recognized on impaired loans, after designation as impaired	[3]	177
Real Estate Construction Portfolio Segment[Member] | Construction, 1-4 Family Residential [Member]
Average recorded investment in impaired loans	[2],[3]			462		612
Income recognized on impaired loans, after designation as impaired	[3]			10		23
Consumer Real Estate Portfolio Segment [Member] | Closed End First Liens [Member]
Average recorded investment in impaired loans	[2],[3]	781		642		681
Income recognized on impaired loans, after designation as impaired	[3]	57		38		43
Consumer Real Estate Portfolio Segment [Member] | Closed End Junior Liens [Member]
Average recorded investment in impaired loans	[2],[3]	185		207		228
Income recognized on impaired loans, after designation as impaired	[3]	11		13		15
Consumer Real Estate Portfolio Segment [Member] | Investor Owned Residential Real Estate [Member]
Average recorded investment in impaired loans	[2],[3]	329		74		76
Income recognized on impaired loans, after designation as impaired	[3]	1		4		5
Commercial Real Estate Portfolio Segment [Member] | Multifamily Real Estate [Member]
Average recorded investment in impaired loans	[2],[3]	748		1,366		2,581
Income recognized on impaired loans, after designation as impaired	[3]	16		12		84
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate, Owner Occupied [Member]
Average recorded investment in impaired loans	[2],[3]	4,047		4,342		6,141
Income recognized on impaired loans, after designation as impaired	[3]	200		206		251
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Average recorded investment in impaired loans	[2],[3]	2,638		3,947		5,888
Income recognized on impaired loans, after designation as impaired	[3]			263		308
Commercial Non Real Estate Segment [Member] | Commercial and Industrial [Member]
Average recorded investment in impaired loans	[2],[3]	1,282		541		1,090
Income recognized on impaired loans, after designation as impaired	[3]	64		7		$ 40
Consumer Non Real Estate Portfolio Segment [Member] | Automobile Loan [Member]
Average recorded investment in impaired loans	[2],[3]	36		4
Income recognized on impaired loans, after designation as impaired	[3]	$ 2		$ 0

[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.