Note 9 - Fair Value Measurement - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Estimated fair value	$ 447,445	$ 489,181
US Treasury Securities [Member]
Estimated fair value	6,919	6,880
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Estimated fair value	229,633	235,931
Commercial Mortgage Backed Securities Issued by US Government Agencies [Member]
Estimated fair value	123,078	115,952
US States and Political Subdivisions Debt Securities [Member]
Estimated fair value	87,815	130,418
Fair Value, Recurring [Member]
Estimated fair value	447,445	489,181
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Estimated fair value	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Estimated fair value	447,445	489,181
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Estimated fair value	0	0
Fair Value, Recurring [Member] \| US Treasury Securities [Member]
Estimated fair value	6,919	6,880
Fair Value, Recurring [Member] \| US Treasury Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Estimated fair value	0	0
Fair Value, Recurring [Member] \| US Treasury Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Estimated fair value	6,919	6,880
Fair Value, Recurring [Member] \| US Treasury Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Estimated fair value	0	0
Fair Value, Recurring [Member] \| Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Estimated fair value	229,633	235,931
Fair Value, Recurring [Member] \| Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Inputs, Level 1 [Member]
Estimated fair value	0	0
Fair Value, Recurring [Member] \| Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Inputs, Level 2 [Member]
Estimated fair value	229,633	235,931
Fair Value, Recurring [Member] \| Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Inputs, Level 3 [Member]
Estimated fair value	0	0
Fair Value, Recurring [Member] \| Commercial Mortgage Backed Securities Issued by US Government Agencies [Member]
Estimated fair value	123,078	115,952
Fair Value, Recurring [Member] \| Commercial Mortgage Backed Securities Issued by US Government Agencies [Member] \| Fair Value, Inputs, Level 1 [Member]
Estimated fair value	0	0
Fair Value, Recurring [Member] \| Commercial Mortgage Backed Securities Issued by US Government Agencies [Member] \| Fair Value, Inputs, Level 2 [Member]
Estimated fair value	123,078	115,952
Fair Value, Recurring [Member] \| Commercial Mortgage Backed Securities Issued by US Government Agencies [Member] \| Fair Value, Inputs, Level 3 [Member]
Estimated fair value	0	0
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member]
Estimated fair value	87,815	130,418
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Estimated fair value	0	0
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Estimated fair value	87,815	130,418
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Estimated fair value	$ 0	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 103
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-103

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481830/320-10-45-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

+ Details