Note 5 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance	$ 8,300	$ 8,297	$ 8,263
Charge-offs	(819)	(1,806)	(2,120)
Recoveries	287	159	145
Provision for loan losses	157	1,650	2,009
Balance	7,925	8,300	8,297
Real Estate Construction Portfolio Segment[Member]
Balance	438	576	612
Charge-offs	0	(29)
Recoveries	0	0	0
Provision for loan losses	(101)	(109)	(36)
Balance	337	438	576
Consumer Real Estate Portfolio Segment [Member]
Balance	1,830	1,866	1,662
Charge-offs	(146)	(133)	(205)
Recoveries	1	2	2
Provision for loan losses	342	95	407
Balance	2,027	1,830	1,866
Commercial Real Estate Portfolio Segment [Member]
Balance	3,738	4,109	3,537
Charge-offs	(139)	(488)	(1,114)
Recoveries	131	83	49
Provision for loan losses	(686)	34	1,637
Balance	3,044	3,738	4,109
Commercial Non Real Estate Segment [Member]
Balance	1,063	655	1,475
Charge-offs	(82)	(883)	(490)
Recoveries	23	10	1
Provision for loan losses	68	(1,281)	(331)
Balance	1,072	1,063	655
Public Sector and IDA Portfolio Segment[Member]
Balance	330	436	327
Charge-offs	0	0	0
Recoveries	0	0	0
Provision for loan losses	89	(106)	109
Balance	419	330	436
Consumer Non Real Estate Portfolio Segment [Member]
Balance	644	627	602
Charge-offs	(452)	(273)	(311)
Recoveries	132	64	93
Provision for loan losses	383	226	243
Balance	707	644	627
Unallocated Financing Receivables [Member]
Balance	257	28	48
Charge-offs	0	0	0
Recoveries	0	0	0
Provision for loan losses	62	229	(20)
Balance	$ 319	$ 257	$ 28