Note 3 - Investment Securities - Investment Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Available for sale debt securities, continuous unrealized loss position less than 12 months, fair value	$ 21,950	$ 34,552
Available for sale debt securities, continuous unrealized loss position less than 12 months, gross unrealized losses	(161)	(506)
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, fair value	17,860	65,876
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, gross unrealized losses	(324)	(1,719)
US Government Corporations and Agencies Securities [Member]
Available for sale debt securities, continuous unrealized loss position less than 12 months, fair value
Available for sale debt securities, continuous unrealized loss position less than 12 months, gross unrealized losses
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, fair value		3,385
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, gross unrealized losses		(44)
US States and Political Subdivisions Debt Securities [Member]
Available for sale debt securities, continuous unrealized loss position less than 12 months, fair value	11,142	17,887
Available for sale debt securities, continuous unrealized loss position less than 12 months, gross unrealized losses	(93)	(140)
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, fair value		32,712
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, gross unrealized losses		(850)
Corporate Debt Securities [Member]
Available for sale debt securities, continuous unrealized loss position less than 12 months, fair value		2,890
Available for sale debt securities, continuous unrealized loss position less than 12 months, gross unrealized losses		(110)
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, fair value	992	7,220
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, gross unrealized losses	(8)	(190)
Mortgage-backed Securities and Collateralized Mortgage Obligations [Member]
Available for sale debt securities, continuous unrealized loss position less than 12 months, fair value	9,868	5,575
Available for sale debt securities, continuous unrealized loss position less than 12 months, gross unrealized losses	(35)	(98)
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, fair value	7,968	22,559
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, gross unrealized losses	(78)	(635)
Asset-backed Securities [Member]
Available for sale debt securities, continuous unrealized loss position less than 12 months, fair value	940	8,200
Available for sale debt securities, continuous unrealized loss position less than 12 months, gross unrealized losses	(33)	(158)
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, fair value	8,900
Available for sale debt securities, continuous unrealized loss position for 12 months or longer, gross unrealized losses	$ (238)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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