Note 1 - Basis of Presentation and Significant Accounting Policies (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Number of Operating Segments	1
Minimum Principal Balance of Loans for Quarterly Rating Review	$ 500
Restructured Loans, Reserves	$ 250
Lessee, Operating Lease, Term of Contract	10 years
Furniture and Fixtures [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	5 years
Furniture and Fixtures [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	10 years
Equipment, Computer Hardware and Software [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	3 years
Equipment, Computer Hardware and Software [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	5 years
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life	7 years
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life	40 years
Land Improvements [Member]
Property, Plant and Equipment, Useful Life	20 years
Other Assets [Member]
Equity Securities without Readily Determinable Fair Value, Amount	$ 3,680		$ 2,200
Operating Lease, Right-of-Use Asset	917,000
Other Assets [Member] | Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset		$ 915
Other Liabilities [Member]
Operating Lease, Liability, Total	1,009
Other Liabilities [Member] | Accounting Standards Update 2016-02 [Member]
Operating Lease, Liability, Total		$ 915
Investment in Federal Home Loan Bank (FHLB) and Federal Reserve Bank (FRB) Stock [Member]
Investment Owned, at Cost	$ 8,900		$ 7,780