Note 6 - Mortgage Loan Servicing (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Continuing Involvement with Transferred Financial Assets Custodial Escrow Balance	$ 4,700	$ 4,600
Valuation Allowance for Impairment of Recognized Servicing Assets, Balance	0	0
Servicing Asset at Fair Value, Amount	$ 8,400	$ 8,000
Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Discount Rate	7.50%	7.01%
Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Prepayment Speed	11.80%	11.50%
Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Expected Credit Losses	0.73%	0.68%
Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Weighted Average Life	3 years 146 days	3 years 219 days