Note 3 - Loans - Types of Troubled Debt Restructuring Loan Modification by Portfolio Segment (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Troubled debt restructuring	$ 466	$ 475
Performing Financial Instruments [Member]
Troubled debt restructuring	466	475
Nonperforming Financial Instruments [Member]
Troubled debt restructuring
Commercial Real Estate Portfolio Segment [Member] | One- to Four-family Residential Properties [Member] | Performing Financial Instruments [Member]
Troubled debt restructuring	391	400
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member]
Troubled debt restructuring	391	400
Commercial Real Estate Portfolio Segment [Member] | Nonfarm Nonresidential [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructuring
Residential Portfolio Segment [Member] | One- to Four-family Residential Properties [Member]
Troubled debt restructuring	75	75
Residential Portfolio Segment [Member] | One- to Four-family Residential Properties [Member] | Performing Financial Instruments [Member]
Troubled debt restructuring	75	75
Residential Portfolio Segment [Member] | One- to Four-family Residential Properties [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructuring