Note 4 - Investment Securities - Continuous Unrealized Loss Positions (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Less than 12 months, fair value	$ 9,635	$ 5,968
Less than 12 months, unrealized losses	(98)	(20)
12 months or more, fair value	1,433	33,850
12 months or more, unrealized losses	(67)	(1,190)
Fair value	11,068	39,818
Unrealized losses	(165)	(1,210)
Collateralized Mortgage Backed Securities [Member]
Less than 12 months, fair value	8,625	450
Less than 12 months, unrealized losses	(97)	(1)
12 months or more, fair value		24,227
12 months or more, unrealized losses		(864)
Fair value	8,625	24,677
Unrealized losses	(97)	(865)
Corporate Debt Securities [Member]
Less than 12 months, fair value
Less than 12 months, unrealized losses
12 months or more, fair value	1,433	2,789
12 months or more, unrealized losses	(67)	(181)
Fair value	1,433	2,789
Unrealized losses	(67)	(181)
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months, fair value	1,010	5,518
Less than 12 months, unrealized losses	(1)	(19)
12 months or more, fair value		6,834
12 months or more, unrealized losses		(145)
Fair value	1,010	12,352
Unrealized losses	$ (1)	$ (164)