Note 3 - Fair Value Measurement - Quantitative Information About Level 3 Fair Value Measurements for Financial Instruments Measured at Fair Value on a Non-recurring Basis (Details)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Residential Portfolio Segment [Member] | Equity Lines of Credit [Member] | Measurement Input, Cost to Sell [Member]
Other real estate, Measurement Input		0.1
Residential Portfolio Segment [Member] | Equity Lines of Credit [Member] | Measurement Input, Cost to Sell [Member] | Weighted Average [Member]
Other real estate, Measurement Input		0.1
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member]
Other real estate, Measurement Input
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Weighted Average [Member]
Other real estate, Measurement Input	0.16
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Minimum [Member]
Other real estate, Measurement Input	0.1
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Maximum [Member]
Other real estate, Measurement Input	0.34
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Weighted Average [Member]
Other real estate, Measurement Input	0.16	0.22
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Minimum [Member]
Other real estate, Measurement Input	0.16	0.17
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Maximum [Member]
Other real estate, Measurement Input	0.17	0.31
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Measurement Input, Cost to Sell [Member]
Other real estate, Measurement Input		0.1
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Measurement Input, Cost to Sell [Member] | Weighted Average [Member]
Other real estate, Measurement Input	0.24	0.1
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Measurement Input, Cost to Sell [Member] | Minimum [Member]
Other real estate, Measurement Input	0.1
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Measurement Input, Cost to Sell [Member] | Maximum [Member]
Other real estate, Measurement Input	0.51
Impaired Loans [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member] | Measurement Input, Cost to Sell [Member]
Impaired loans, Measurement Input		0.08
Impaired Loans [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member] | Measurement Input, Cost to Sell [Member] | Weighted Average [Member]
Impaired loans, Measurement Input		0.08
Fair Value, Measurements, Nonrecurring [Member]
Impaired loans		$ 80,000
Other real estate		1,344,000
Fair Value, Measurements, Nonrecurring [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Impaired loans		80,000
Other real estate		90,000
Fair Value, Measurements, Nonrecurring [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Other real estate	368,000
Fair Value, Measurements, Nonrecurring [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Other real estate	347,000	285,000
Fair Value, Measurements, Nonrecurring [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Other real estate	455,000	969,000
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Impaired loans		$ 80,000