Note 3 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Less than 12 months, fair value	$ 17,642	$ 46,564
Less than 12 months, unrealized loss	(379)	(606)
12 months or more, fair value	7,291	16,477
12 months or more, unrealized loss	(63)	(218)
Total, fair value	24,933	63,041
Total, unrealized loss	(442)	(824)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Less than 12 months, fair value	3,425	14,578
Less than 12 months, unrealized loss	(11)	(76)
12 months or more, fair value		2,325
12 months or more, unrealized loss		(8)
Total, fair value	3,425	16,903
Total, unrealized loss	(11)	(84)
Collateralized Mortgage Obligations [Member]
Less than 12 months, fair value	2,973	12,319
Less than 12 months, unrealized loss	(8)	(32)
12 months or more, fair value	5,175	11,621
12 months or more, unrealized loss	(6)	(203)
Total, fair value	8,148	23,940
Total, unrealized loss	(14)	(235)
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months, fair value	6,725	15,636
Less than 12 months, unrealized loss	(128)	(269)
12 months or more, fair value	1,641
12 months or more, unrealized loss	(32)
Total, fair value	8,366	15,636
Total, unrealized loss	(160)	(269)
Corporate Debt Securities [Member]
Less than 12 months, fair value	4,519	4,031
Less than 12 months, unrealized loss	(232)	(229)
12 months or more, fair value	475	499
12 months or more, unrealized loss	(25)	(1)
Total, fair value	4,994	4,530
Total, unrealized loss	$ (257)	(230)
US Government Agencies Debt Securities [Member]
Less than 12 months, fair value
Less than 12 months, unrealized loss
12 months or more, fair value		2,032
12 months or more, unrealized loss		(6)
Total, fair value		2,032
Total, unrealized loss		$ (6)