Note 5 - Loans - Average Recorded Investment and Interest Income Recognized on Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Average recorded investment	$ 15,585	$ 18,323	$ 25,299
Interest income recognized	275	286	298
Commercial Portfolio Segment [Member]
Average recorded investment	3,211	2,605	3,533
Interest income recognized	46	23	22
Commercial Portfolio Segment [Member] | Commercial Owner Occupied Loan [Member]
Interest income recognized	2
Commercial Real Estate Portfolio Segment [Member] | Commercial Non-owner Occupied [Member]
Average recorded investment	1,548	2,013	7,306
Interest income recognized	46	47	49
Commercial Real Estate Portfolio Segment [Member] | Commercial Owner Occupied Loan [Member]
Average recorded investment	670	1,281	2,212
Interest income recognized		25	59
Residential Portfolio Segment [Member] | Individual Tax Identification Number Loan [Member]
Average recorded investment	7,961	8,939	9,679
Interest income recognized	162	165	141
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Mortgage Receivable [Member]
Average recorded investment	1,019	1,788	1,786
Interest income recognized
Residential Portfolio Segment [Member] | Home Equity Loan [Member]
Average recorded investment	1,104	1,535	750
Interest income recognized	19	26	27
Consumer Portfolio Segment [Member]
Average recorded investment	72	162	33
Interest income recognized