Note 2 - Securities - Debt Securities by Maturity (Details)	Mar. 31, 2018 USD ($)
Due in 2018	1.86%
Due in 2018	$ 28,193,000
Due in 2018	$ 28,181,000
Due in 2019 through 2023	2.12%
Due in 2019 through 2023	$ 65,051,000
Due in 2019 through 2023	$ 64,576,000
Due in 2024 through 2028	2.52%
Due in 2024 through 2028	$ 99,189,000
Due in 2024 through 2028	$ 94,685,000
Due in 2029 and beyond	2.95%
Due in 2029 and beyond	$ 114,780,000
Due in 2029 and beyond	$ 107,230,000
Total available for sale securities	2.51%
Total available for sale securities	$ 350,335,000
Total available for sale securities	$ 336,988,000
Collateralized Mortgage Backed Securities [Member]
No single maturity, weighted average yield	2.33%
No single maturity, amortized cost	$ 41,104,000
No single maturity, fair value	$ 40,351,000
Other Debt and Equity Securities [Member]
No single maturity, weighted average yield	2.84%
No single maturity, amortized cost	$ 2,018,000
No single maturity, fair value	$ 1,965,000

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), 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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