Note 11 - Fair Value of Financial Instruments - Quantitative Information About Non-recurring Level 3 Fair Value of Financial Instruments and the Fair Value Measurements (Details) $ in Thousands	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Impaired loans, Measurement Input	0.15	0
Fair Value, Nonrecurring [Member]
Impaired loans	$ 1,928	$ 4,111
Valuation, Income Approach [Member] | Measurement Input, Cap Rate [Member]
Impaired loans, Measurement Input		8.5
Valuation, Income Approach [Member] | Measurement Input, Cap Rate [Member] | Minimum [Member]
Impaired loans, Measurement Input	0.2
Valuation, Income Approach [Member] | Measurement Input, Cap Rate [Member] | Maximum [Member]
Impaired loans, Measurement Input	0.545
Valuation, Income Approach [Member] | Measurement Input, Cap Rate [Member] | Weighted Average [Member]
Impaired loans, Measurement Input	0.396	8.5
Valuation, Income Approach [Member] | Measurement Input, Loss Severity [Member]
Impaired loans, Measurement Input	0.095	15
Valuation, Income Approach [Member] | Measurement Input, Loss Severity [Member] | Weighted Average [Member]
Impaired loans, Measurement Input	0.095	15
Valuation, Income Approach [Member] | Fair Value, Nonrecurring [Member] | Measurement Input, Cap Rate [Member]
Impaired loans	$ 1,656	$ 204
Valuation, Market Approach [Member] | Measurement Input, Comparability Adjustment [Member] | Minimum [Member]
Impaired loans, Measurement Input	(0.1)
Valuation, Market Approach [Member] | Measurement Input, Comparability Adjustment [Member] | Maximum [Member]
Impaired loans, Measurement Input	0.15
Valuation, Market Approach [Member] | Measurement Input, Comparability Adjustment [Member] | Weighted Average [Member]
Impaired loans, Measurement Input	0.025	0
Valuation, Market Approach [Member] | Measurement Input, Loss Severity [Member] | Minimum [Member]
Impaired loans, Measurement Input		(36.5)
Valuation, Market Approach [Member] | Measurement Input, Loss Severity [Member] | Maximum [Member]
Impaired loans, Measurement Input		15
Valuation, Market Approach [Member] | Measurement Input, Loss Severity [Member] | Weighted Average [Member]
Impaired loans, Measurement Input	0.15	10.4
Valuation, Market Approach [Member] | Fair Value, Nonrecurring [Member]
Impaired loans	$ 272	$ 2,724
Blended Income and Sales Approach [Member] | Measurement Input, Cap Rate [Member] | Minimum [Member]
Impaired loans, Measurement Input		7.4
Blended Income and Sales Approach [Member] | Measurement Input, Cap Rate [Member] | Maximum [Member]
Impaired loans, Measurement Input		9.8
Blended Income and Sales Approach [Member] | Measurement Input, Cap Rate [Member] | Weighted Average [Member]
Impaired loans, Measurement Input		8.7
Blended Income and Sales Approach [Member] | Measurement Input, Comparability Adjustment [Member] | Minimum [Member]
Impaired loans, Measurement Input		(30)
Blended Income and Sales Approach [Member] | Measurement Input, Comparability Adjustment [Member] | Maximum [Member]
Impaired loans, Measurement Input		10
Blended Income and Sales Approach [Member] | Measurement Input, Comparability Adjustment [Member] | Weighted Average [Member]
Impaired loans, Measurement Input		(7.8)
Blended Income and Sales Approach [Member] | Measurement Input, Loss Severity [Member]
Impaired loans, Measurement Input		15
Blended Income and Sales Approach [Member] | Measurement Input, Loss Severity [Member] | Weighted Average [Member]
Impaired loans, Measurement Input		15
Blended Income and Sales Approach [Member] | Fair Value, Nonrecurring [Member]
Impaired loans		$ 1,183
Sales Approach Valuation Technique [Member]
Other repossessed assets		$ 35
Other repossessed assets, Measurement Input		0
Sales Approach Valuation Technique [Member] | Measurement Input, Loss Severity [Member] | Weighted Average [Member]
Other repossessed assets, Measurement Input		0