Note 3 - Available-for-sale Securities - Investment Securities in a Continuous Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Available-for-sale securities in continuous loss position, less than 12 months, fair value	$ 13,937	$ 7,724
Available-for-sale securities in continuous loss position, less than 12 months, unrealized loss	(521)	(62)
Available-for-sale securities in continuous loss position, 12 months or more, fair value	13,341	17,081
Available-for-sale securities in continuous loss position, 12 months or more, unrealized loss	(2,261)	(886)
Available-for-sale securities in continuous loss position, fair value	27,278	24,805
Available-for-sale securities in continuous loss position, unrealized loss	(2,782)	(948)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities in continuous loss position, less than 12 months, fair value	107	2,609
Available-for-sale securities in continuous loss position, less than 12 months, unrealized loss	(4)	(20)
Available-for-sale securities in continuous loss position, 12 months or more, fair value	1,585	3,919
Available-for-sale securities in continuous loss position, 12 months or more, unrealized loss	(17)	(48)
Available-for-sale securities in continuous loss position, fair value	1,692	6,528
Available-for-sale securities in continuous loss position, unrealized loss	(21)	(68)
Corporate Debt Securities [Member]
Available-for-sale securities in continuous loss position, less than 12 months, fair value	3,739
Available-for-sale securities in continuous loss position, less than 12 months, unrealized loss	(278)
Available-for-sale securities in continuous loss position, 12 months or more, fair value	11,756	13,162
Available-for-sale securities in continuous loss position, 12 months or more, unrealized loss	(2,244)	(838)
Available-for-sale securities in continuous loss position, fair value	15,495	13,162
Available-for-sale securities in continuous loss position, unrealized loss	(2,522)	(838)
Subordinated Notes [Member]
Available-for-sale securities in continuous loss position, less than 12 months, fair value	5,321
Available-for-sale securities in continuous loss position, less than 12 months, unrealized loss	(204)
Available-for-sale securities in continuous loss position, 12 months or more, fair value
Available-for-sale securities in continuous loss position, 12 months or more, unrealized loss
Available-for-sale securities in continuous loss position, fair value	5,321
Available-for-sale securities in continuous loss position, unrealized loss	(204)
SBA Loan Pools [Member]
Available-for-sale securities in continuous loss position, less than 12 months, fair value	4,770	5,115
Available-for-sale securities in continuous loss position, less than 12 months, unrealized loss	(35)	(42)
Available-for-sale securities in continuous loss position, 12 months or more, fair value
Available-for-sale securities in continuous loss position, 12 months or more, unrealized loss
Available-for-sale securities in continuous loss position, fair value	4,770	5,115
Available-for-sale securities in continuous loss position, unrealized loss	$ (35)	$ (42)