Note 2 - Securities - Debt Securities by Maturity (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Due in 2018, weighted average yield	1.69%
Due in 2018, amortized cost	$ 6,400,000
Due in 2018, fair value	$ 6,397,000
Due in 2019 through 2023, weighted average yield	2.17%
Due in 2019 through 2023, amortized cost	$ 77,542,000
Due in 2019 through 2023, fair value	$ 76,463,000
Due in 2024 through 2028, weighted average yield	2.60%
Due in 2024 through 2028, amortized cost	$ 106,528,000
Due in 2024 through 2028, fair value	$ 100,317,000
Due in 2029 and beyond, weighted average yield	3.07%
Due in 2029 and beyond, amortized cost	$ 109,745,000
Due in 2029 and beyond, fair value	$ 101,217,000
Total available for sale securities, weighted average yield	2.64%
Securities available for sale, amortized cost	$ 343,434,000	$ 341,948,000
Securities available for sale, fair value	$ 326,531,000	335,744,000
Collateralized Mortgage Backed Securities [Member]
No single maturity, weighted average yield	2.60%
No single maturity, amortized cost	$ 42,719,000
No single maturity, fair value	41,637,000
Securities available for sale, amortized cost	42,719,000	38,967,000
Securities available for sale, fair value	$ 41,637,000	38,792,000
Other Debt and Equity Securities [Member]
No single maturity, weighted average yield	3.94%
No single maturity, amortized cost	$ 500,000
No single maturity, fair value	500,000
Securities available for sale, amortized cost	500,000	2,010,000
Securities available for sale, fair value	$ 500,000	$ 1,981,000

The aggregate weighted average yield of a securities portfolio.

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The weighted average yield of a securities portfolio with due dates after 10 years.

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The weighted average yield of a securities portfolio with due dates before 5 years and before 10 years.

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The weighted average yield of a securities portfolio with due dates after 1 year and before 5 years.

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The weighted average yield of securities portfolio with due dates in less than 1 year.

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The weighted average yield of a securities portfolio with no single maturity date defined.

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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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-Publisher FASB
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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), with single maturity date and allocated without single maturity date, maturing in sixth fiscal year through tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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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), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in second through fifth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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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), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing after tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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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), with single maturity date and allocated without single maturity date, maturing in remainder of fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in remainder of fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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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), without single maturity date and not allocated over maturity grouping.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), without single maturity date and not allocated over maturity grouping.

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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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