Note 2 - Fair Value of Financial Instruments - Level 3 Fair Value Measurements (Details) - Fair Value, Nonrecurring [Member] - Valuation, Market Approach [Member] $ in Thousands	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Commercial and Industrial Portfolio Segment [Member]
Impaired Loans, Fair Value	$ 777	$ 4,559
Commercial and Industrial Portfolio Segment [Member] | Minimum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired Loans, Measurement Input	0.24	0
Commercial and Industrial Portfolio Segment [Member] | Maximum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired Loans, Measurement Input	0.5	0.61
Commercial and Industrial Portfolio Segment [Member] | Weighted Average [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired Loans, Measurement Input	0.289	0.103
Commercial Real Estate Owner Occupied [Member] | Commercial Portfolio Segment [Member]
Impaired Loans, Fair Value	$ 459	$ 1,644
Commercial Real Estate Owner Occupied [Member] | Commercial Portfolio Segment [Member] | Minimum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired Loans, Measurement Input	0.1	0
Commercial Real Estate Owner Occupied [Member] | Commercial Portfolio Segment [Member] | Maximum [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired Loans, Measurement Input	0.5	0.2
Commercial Real Estate Owner Occupied [Member] | Commercial Portfolio Segment [Member] | Weighted Average [Member] | Measurement Input, Comparability Adjustment [Member]
Impaired Loans, Measurement Input	0.278	0.097