Note 2 - Securities - Debt Securities by Maturity (Details)	Jun. 30, 2017 USD ($)
Due in 2017	1.26%
Due in 2017	$ 10,132,000
Due in 2017	$ 10,140,000
Due in 2018 through 2022	2.21%
Due in 2018 through 2022	$ 95,647,000
Due in 2018 through 2022	$ 96,263,000
Due in 2023 through 2027	2.69%
Due in 2023 through 2027	$ 97,643,000
Due in 2023 through 2027	$ 97,182,000
Due in 2028 and beyond	2.88%
Due in 2028 and beyond	$ 78,259,000
Due in 2028 and beyond	$ 76,501,000
Total available for sale securities	2.44%
Available-for-sale Debt Securities, Amortized Cost Basis	$ 323,548,000
Total available for sale securities	$ 322,258,000
Collateralized Mortgage Backed Securities [Member]
No single maturity, weighted average yield	1.87%
No single maturity, amortized cost	$ 39,873,000
No single maturity, fair value	$ 40,199,000
Other Debt and Equity Securities [Member]
No single maturity, weighted average yield	1.32%
No single maturity, amortized cost	$ 1,994,000
No single maturity, fair value	$ 1,973,000