Note 6 - Investment Securities (Details Textual)	3 Months Ended	9 Months Ended
Sep. 30, 2020 USD ($) security	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) security	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Investment Securities [Line Items]
Proceeds from sale of investment securities	$ 0	$ 9,511,000	$ 6,931,000	$ 30,294,000
Available-for-sale securities pledged as collateral	$ 245,184,000		$ 245,184,000		$ 205,016,000
Debt Securities, Available-for-sale, Restriction Type [Extensible List]	us-gaap:CollateralPledgedMember		us-gaap:CollateralPledgedMember		us-gaap:CollateralPledgedMember
Available-for-sale, amortized cost	$ 437,863,000		$ 437,863,000		$ 349,385,000
Fair value	444,616,000		444,616,000		349,710,000
Investment equity securities	11,691,000		11,691,000		$ 9,164,000
Proceeds from the sale of equity securities	$ 2,266,000	6,404,000	$ 3,694,000	10,924,000
PreTSL [Member]
Investment Securities [Line Items]
Number of trust preferred securities \| security	1		1
Available-for-sale, amortized cost	$ 84,000		$ 84,000
Fair value	68,000		68,000
Equity Securities [Member]
Investment Securities [Line Items]
Income tax expense (benefit) related to net recognized gains (losses) on sales of securities	234,000	192,000	(230,000)	539,000
Debt Securities [Member]
Investment Securities [Line Items]
Income tax benefit related to net realized gains (losses) on sales of securities	3,000	0	$ 3,000	$ (8,000)
Other than temporary impairment, credit losses recognized in earnings	$ 0	$ 0

Income tax expense (benefit) during the period related to net realized gains (losses) on sales of securities.

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Income tax expense (benefit) during the period related to net recognized gains (losses) on sales of securities.

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Investment securities.

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The number of trust preferred securities held by the entity.

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Proceeds from sale of investment in equity securities.

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

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

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

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

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which a previous OTTI was recognized and the investor does not intend to sell the debt security and it is not more likely than not that the investor will be required to sell the debt security before recovery of its amortized cost basis.

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

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