Note 10 - Fair Values Measurement - Financial Assets Measured at the Fair Value on Recurring and Non-recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Securities available for sale	$ 198,657	$ 209,000
Recorded investment, total	2,144	2,170
Fair Value, Recurring [Member]
Securities available for sale	198,657	209,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	198,657	209,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale
US Treasury and Government [Member]
Securities available for sale	21,104	22,330
US Treasury and Government [Member] | Fair Value, Recurring [Member]
Securities available for sale	21,104	22,330
US Treasury and Government [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale
US Treasury and Government [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	21,104	22,330
US Treasury and Government [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Commercial Portfolio Segment [Member]
Recorded investment, total		21
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member]
Recorded investment, total
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member]
Recorded investment, total
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member]
Recorded investment, total		21
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Farmland Loans [Member]
Recorded investment, total	124	245
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Farmland Loans [Member]
Recorded investment, total
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Farmland Loans [Member]
Recorded investment, total
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Farmland Loans [Member]
Recorded investment, total	124	245
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Residential Portfolio Segment [Member] | One- to Four-family Residential Properties [Member]
Recorded investment, total	74	145
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Residential Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | One- to Four-family Residential Properties [Member]
Recorded investment, total
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Residential Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | One- to Four-family Residential Properties [Member]
Recorded investment, total
Impaired Loans [Member] | Fair Value, Nonrecurring [Member] | Residential Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | One- to Four-family Residential Properties [Member]
Recorded investment, total	74	145
Residential Mortgage Backed Securities [Member]
Securities available for sale	89,101	92,200
Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member]
Securities available for sale	89,101	92,200
Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale
Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	89,101	92,200
Residential Mortgage Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale
Collateralized Debt Obligations [Member]
Securities available for sale	40,754	49,419
Collateralized Debt Obligations [Member] | Fair Value, Recurring [Member]
Securities available for sale	40,754	49,419
Collateralized Debt Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale
Collateralized Debt Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	40,754	49,419
Collateralized Debt Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale
US States and Political Subdivisions Debt Securities [Member]
Securities available for sale	28,154	28,366
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member]
Securities available for sale	28,154	28,366
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	28,154	28,366
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale
Corporate Debt Securities [Member]
Securities available for sale	19,544	16,685
Corporate Debt Securities [Member] | Fair Value, Recurring [Member]
Securities available for sale	19,544	16,685
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available for sale
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available for sale	19,544	16,685
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available for sale