Note 9 - Fair Value Measurements - Quantitative Information About Level 3 Fair Value Measurements for Financial Instruments Measured at Fair Value on a Non-recurring Basis (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Assets Fair Value Disclosure Nonrecurring	$ 1,396	$ 1,271
Impaired Loans [Member]
Assets Fair Value Disclosure Nonrecurring	552	536
Other Real Estate [Member]
Assets Fair Value Disclosure Nonrecurring	$ 844	$ 735
Commercial Portfolio Segment [Member] | Impaired Loans [Member] | Maximum [Member]
Impaired loans, other real estate - unobservable input range	36.00%	36.00%
Commercial Portfolio Segment [Member] | Impaired Loans [Member] | Weighted Average [Member]
Impaired loans, other real estate - unobservable input range	33.00%	33.00%
Commercial Portfolio Segment [Member] | Impaired Loans [Member] | Minimum [Member]
Impaired loans, other real estate - unobservable input range	10.00%	10.00%
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Impaired Loans [Member]
Assets Fair Value Disclosure Nonrecurring	$ 450	$ 453
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Impaired Loans [Member] | Maximum [Member]
Impaired loans, other real estate - unobservable input range	12.00%	12.00%
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Impaired Loans [Member] | Weighted Average [Member]
Impaired loans, other real estate - unobservable input range	12.00%	12.00%
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Other Real Estate [Member]
Assets Fair Value Disclosure Nonrecurring	$ 193	$ 84
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Other Real Estate [Member] | Maximum [Member]
Impaired loans, other real estate - unobservable input range	7.00%	40.00%
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Other Real Estate [Member] | Weighted Average [Member]
Impaired loans, other real estate - unobservable input range	7.00%	40.00%
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Impaired Loans [Member]
Assets Fair Value Disclosure Nonrecurring	$ 641	$ 641
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Other Real Estate [Member]
Assets Fair Value Disclosure Nonrecurring	641	641
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Impaired Loans [Member]
Assets Fair Value Disclosure Nonrecurring	$ 102	$ 83
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Impaired Loans [Member] | Maximum [Member]
Impaired loans, other real estate - unobservable input range	10.00%	8.00%
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Impaired Loans [Member] | Weighted Average [Member]
Impaired loans, other real estate - unobservable input range	8.00%	8.00%
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Impaired Loans [Member] | Minimum [Member]
Impaired loans, other real estate - unobservable input range	8.00%
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Other Real Estate [Member]
Assets Fair Value Disclosure Nonrecurring	$ 10	$ 10
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Other Real Estate [Member] | Maximum [Member]
Impaired loans, other real estate - unobservable input range	48.00%	48.00%
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Other Real Estate [Member] | Weighted Average [Member]
Impaired loans, other real estate - unobservable input range	48.00%	48.00%