Note 4 - Loans and Allowance for Loan Losses - Activity In the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance at beginning of period				$ 9,344				$ 10,315	$ 9,344	$ 10,315	$ 13,968
Provision for loan losses	$ 87	$ (379)	$ (499)	580	$ 175	$ (190)	$ (156)	(473)	(211)	(644)	(3,429)
Recoveries									1,580	413	785
Loans charged off									(930)	(740)	(1,009)
Balance at end of period	9,783				9,344				9,783	9,344	10,315
Real Estate Portfolio Segment [Member]
Balance at beginning of period				8,205				9,173	8,205	9,173	12,542
Provision for loan losses									(537)	(702)	(3,099)
Recoveries									1,386	141	463
Loans charged off									(545)	(407)	(733)
Balance at end of period	8,509				8,205				8,509	8,205	9,173
Commercial Portfolio Segment [Member]
Balance at beginning of period				854				820	854	820	1,153
Provision for loan losses									237	50	(449)
Recoveries									139	203	210
Loans charged off									(279)	(219)	(94)
Balance at end of period	951				854				951	854	820
Consumer Portfolio Segment [Member]
Balance at beginning of period				$ 285				$ 322	285	322	273
Provision for loan losses									89	8	119
Recoveries									55	69	112
Loans charged off									(106)	(114)	(182)
Balance at end of period	$ 323				$ 285				$ 323	$ 285	$ 322