Note 4 - Loans and Allowance for Loan Losses - Nonaccrual Loans and Loans Past Due 90 Days or More and Still Accruing (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Loans past due 90 days and still accruing	$ 395	$ 334
Nonaccrual	12,130	10,112
Commercial real estate:
Loans past due 90 days and still accruing	395	334
Nonaccrual	12,130	10,112
Consumer:
Loans past due 90 days and still accruing	395	334
Nonaccrual	12,130	10,112
Residential Portfolio Segment [Member]
Loans past due 90 days and still accruing	121	131
Nonaccrual	7,794	5,906
Commercial real estate:
Loans past due 90 days and still accruing	121	131
Nonaccrual	7,794	5,906
Consumer:
Loans past due 90 days and still accruing	121	131
Nonaccrual	7,794	5,906
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Owner Occupied [Member]
Loans past due 90 days and still accruing
Nonaccrual	652	476
Commercial real estate:
Loans past due 90 days and still accruing
Nonaccrual	652	476
Consumer:
Loans past due 90 days and still accruing
Nonaccrual	652	476
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Nonowner Occupied [Member]
Loans past due 90 days and still accruing
Nonaccrual	2,432	2,454
Commercial real estate:
Loans past due 90 days and still accruing
Nonaccrual	2,432	2,454
Consumer:
Loans past due 90 days and still accruing
Nonaccrual	2,432	2,454
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Loans past due 90 days and still accruing
Nonaccrual	424	444
Commercial real estate:
Loans past due 90 days and still accruing
Nonaccrual	424	444
Consumer:
Loans past due 90 days and still accruing
Nonaccrual	424	444
Commercial and Industrial Portfolio Segment [Member]
Loans past due 90 days and still accruing	31
Nonaccrual	396	337
Commercial real estate:
Loans past due 90 days and still accruing	31
Nonaccrual	396	337
Consumer:
Loans past due 90 days and still accruing	31
Nonaccrual	396	337
Consumer Portfolio Segment [Member] | Automobile Loan [Member]
Loans past due 90 days and still accruing	154	127
Nonaccrual	59	86
Commercial real estate:
Loans past due 90 days and still accruing	154	127
Nonaccrual	59	86
Consumer:
Loans past due 90 days and still accruing	154	127
Nonaccrual	59	86
Consumer Portfolio Segment [Member] | Home Equity Loan [Member]
Loans past due 90 days and still accruing
Nonaccrual	260	283
Commercial real estate:
Loans past due 90 days and still accruing
Nonaccrual	260	283
Consumer:
Loans past due 90 days and still accruing
Nonaccrual	260	283
Consumer Portfolio Segment [Member] | Other Consumer Loans [Member]
Loans past due 90 days and still accruing	89	76
Nonaccrual	113	126
Commercial real estate:
Loans past due 90 days and still accruing	89	76
Nonaccrual	113	126
Consumer:
Loans past due 90 days and still accruing	89	76
Nonaccrual	$ 113	$ 126