Note 3 - Investment Securities - Securities Held to Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Securities held to maturity, amortized cost	$ 25,149	$ 47,133
Securities held to maturity, unrealized gains		135
Securities held to maturity, unrealized losses	(65)	(2)
Securities held to maturity, fair value	25,084	47,266
US Government Agencies Debt Securities [Member]
Securities held to maturity, amortized cost	17,937	36,741
Securities held to maturity, unrealized gains		124
Securities held to maturity, unrealized losses	(49)
Securities held to maturity, fair value	17,888	36,865
Corporate Debt Securities [Member]
Securities held to maturity, amortized cost	7,212	10,392
Securities held to maturity, unrealized gains		11
Securities held to maturity, unrealized losses	(16)	(2)
Securities held to maturity, fair value	$ 7,196	$ 10,401

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.6)
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