Note 3 - Fair Value Measurements - Quantitative Information About Level 3 Fair Value Measurements for Financial Instruments Measured at Fair Value on a Non-recurring Basis (Details)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member]
Other real estate, Measurement Input	0.17
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Minimum [Member]
Impaired loans, Measurement Input	0.1
Other real estate, Measurement Input		0.17
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Maximum [Member]
Impaired loans, Measurement Input		0.1
Other real estate, Measurement Input	0.16
Commercial Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Weighted Average [Member]
Other real estate, Measurement Input	0.16	0.16
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Measurement Input, Cost to Sell [Member] | Minimum [Member]
Other real estate, Measurement Input	0.1	0.51
Commercial Portfolio Segment [Member] | Construction Loans [Member] | Measurement Input, Cost to Sell [Member] | Maximum [Member]
Other real estate, Measurement Input	0.1	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
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Minimum [Member]
Other real estate, Measurement Input		0.34
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Maximum [Member]
Other real estate, Measurement Input	0.1
Residential Portfolio Segment [Member] | Real Estate Loan [Member] | Measurement Input, Cost to Sell [Member] | Weighted Average [Member]
Other real estate, Measurement Input		0.16
Fair Value, Nonrecurring [Member]
Impaired loans	$ 130,000
Other real estate	707,000
Fair Value, Nonrecurring [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Impaired loans	130,000
Other real estate	347,000	347,000
Fair Value, Nonrecurring [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Other real estate	360,000	455,000
Fair Value, Nonrecurring [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Other real estate		$ 368,000