Note 4 - Debt Securities Available-for-Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	$ 349,710	$ 344,221
Investment securities available-for-sale, debt securities gross unrealized holding gains	1,602	394
Investment securities available-for-sale, debt securities gross unrealized holding losses	(1,277)	(9,422)
Investment securities available-for-sale, debt securities amortized cost	349,385	353,249
US Government Agencies Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	69,298	68,409
Investment securities available-for-sale, debt securities gross unrealized holding gains	8
Investment securities available-for-sale, debt securities gross unrealized holding losses	(213)	(2,072)
Investment securities available-for-sale, debt securities amortized cost	69,503	70,481
US States and Political Subdivisions Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	50,781	66,313
Investment securities available-for-sale, debt securities gross unrealized holding gains	860	195
Investment securities available-for-sale, debt securities gross unrealized holding losses	(19)	(464)
Investment securities available-for-sale, debt securities amortized cost	49,940	66,582
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	134,829	125,913
Investment securities available-for-sale, debt securities gross unrealized holding gains	371	79
Investment securities available-for-sale, debt securities gross unrealized holding losses	(504)	(4,251)
Investment securities available-for-sale, debt securities amortized cost	134,962	130,085
Collateralized Mortgage Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	86,610	75,491
Investment securities available-for-sale, debt securities gross unrealized holding gains	260	87
Investment securities available-for-sale, debt securities gross unrealized holding losses	(535)	(2,549)
Investment securities available-for-sale, debt securities amortized cost	86,885	77,953
Collateralized Debt Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	79	116
Investment securities available-for-sale, debt securities gross unrealized holding losses	(6)	(6)
Investment securities available-for-sale, debt securities amortized cost	85	122
Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, debt securities	8,113	7,979
Investment securities available-for-sale, debt securities gross unrealized holding gains	103	33
Investment securities available-for-sale, debt securities gross unrealized holding losses		(80)
Investment securities available-for-sale, debt securities amortized cost	$ 8,010	$ 8,026

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amortized cost 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 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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=118942338&loc=SL82898722-210454

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: 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=118954083&loc=d3e26610-111562

Reference 3: 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=118939692&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CollateralizedMortgageObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CollateralizedDebtObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: