Note 11 - Assets and Liabilities Measured and Reported at Fair Value - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Securities available-for-sale	$ 672,167	$ 586,978
Fair Value, Recurring [Member]
Securities available-for-sale	672,167	586,978
Interest rate swaps	4,080	8,374
Total assets	676,247	595,352
Interest rate swaps	4,213	8,391
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
Interest rate swaps	0	0
Total assets	0	0
Interest rate swaps	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	672,167	586,978
Interest rate swaps	4,080	8,374
Total assets	676,247	595,352
Interest rate swaps	4,213	8,391
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Interest rate swaps	0	0
Total assets	0	0
Interest rate swaps	0	0
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale	130,724	138,078
US Government-sponsored Enterprises Debt Securities [Member] \| Fair Value, Recurring [Member]
Securities available-for-sale	130,724	138,078
US Government-sponsored Enterprises Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
US Government-sponsored Enterprises Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	130,724	138,078
US Government-sponsored Enterprises Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale	523,131	437,585
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Recurring [Member]
Securities available-for-sale	523,131	437,585
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	523,131	437,585
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale	18,312	11,315
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member]
Securities available-for-sale	18,312	11,315
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	18,312	11,315
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26610-111562

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

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- Definition

Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

+ References

No definition available.

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- Definition

Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

+ References

No definition available.

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