Note 2 - Securities - Debt Securities by Maturity (Details)	Sep. 30, 2017 USD ($)
Due in 2017	1.51%
Due in 2017	$ 3,307,000
Due in 2017	$ 3,307,000
Due in 2018 through 2022	2.20%
Due in 2018 through 2022	$ 95,857,000
Due in 2018 through 2022	$ 96,451,000
Due in 2023 through 2027	2.71%
Due in 2023 through 2027	$ 99,198,000
Due in 2023 through 2027	$ 98,217,000
Due in 2028 and beyond	2.94%
Due in 2028 and beyond	$ 93,091,000
Due in 2028 and beyond	$ 90,637,000
Total available for sale securities	2.53%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 332,759,000
Total available for sale securities	$ 330,090,000
Collateralized Mortgage Backed Securities [Member]
No single maturity, weighted average yield	2.06%
No single maturity, amortized cost	$ 39,304,000
No single maturity, fair value	$ 39,495,000
Other Debt and Equity Securities [Member]
No single maturity, weighted average yield	2.03%
No single maturity, amortized cost	$ 2,002,000
No single maturity, fair value	$ 1,983,000