Note 9 - Fair Value Measurement - Quantitative Information About Level 3 Fair Value Measurements for Financial Instruments Measured at Fair Value on a Non-Recurring Basis (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Impaired Loans [Member] | Weighted Average [Member]
Impaired loans, other real estate - unobservable input range	12.00%	10.00%
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Impaired Loans [Member] | Minimum [Member]
Impaired loans, other real estate - unobservable input range		9.00%
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Impaired Loans [Member] | Maximum [Member]
Impaired loans, other real estate - unobservable input range		12.00%
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Impaired Loans [Member]
Impaired loans, other real estate	$ 451	$ 1,214
Impaired loans, other real estate - unobservable input range	12.00%
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Other Real Estate [Member] | Weighted Average [Member]
Impaired loans, other real estate - unobservable input range	20.00%	10.00%
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Other Real Estate [Member]
Impaired loans, other real estate	$ 1,000	$ 156
Impaired loans, other real estate - unobservable input range	20.00%	10.00%
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Impaired Loans [Member] | Weighted Average [Member]
Impaired loans, other real estate - unobservable input range	10.00%	8.00%
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Impaired Loans [Member]
Impaired loans, other real estate	$ 22	$ 30
Impaired loans, other real estate - unobservable input range	10.00%	8.00%
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Other Real Estate [Member] | Weighted Average [Member]
Impaired loans, other real estate - unobservable input range	25.00%	10.00%
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Other Real Estate [Member] | Minimum [Member]
Impaired loans, other real estate - unobservable input range	10.00%
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Other Real Estate [Member] | Maximum [Member]
Impaired loans, other real estate - unobservable input range	36.00%
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Other Real Estate [Member]
Impaired loans, other real estate	$ 1,517	$ 1,516
Impaired loans, other real estate - unobservable input range		10.00%
Commercial Portfolio Segment [Member] | Impaired Loans [Member]
Impaired loans, other real estate
Commercial Portfolio Segment [Member] | Other Real Estate [Member]
Impaired loans, other real estate
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]
Impaired loans, other real estate	$ 83	$ 83
Impaired loans, other real estate - unobservable input range	8.00%	8.00%
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Other Real Estate [Member] | Weighted Average [Member]
Impaired loans, other real estate - unobservable input range		10.00%
Consumer Portfolio Segment [Member] | Home Equity Loan [Member] | Other Real Estate [Member]
Impaired loans, other real estate		$ 84
Impaired loans, other real estate - unobservable input range		10.00%
Impaired Loans [Member]
Impaired loans, other real estate	$ 556	$ 1,327
Other Real Estate [Member]
Impaired loans, other real estate	2,517	1,756
Impaired loans, other real estate	$ 3,073	$ 3,083