Note 3 - Securities (Details Textual) - USD ($)		3 Months Ended				9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2007
Pledged Assets Separately Reported, Securities Pledged as Collateral, at Fair Value, Total		$ 1,200,000				$ 1,200,000		$ 2,000,000.0
Equity Securities, FV-NI, Gain (Loss), Total	[1]	$ 0	$ 0			$ 0	$ 295,000
Visa Inc Class B Common Stock [Member]
Equity Securities without Readily Determinable Fair Value, Shares (in shares)				25,702					51,404
Equity Securities without Readily Determinable Fair Value, Shares Sold (in shares)					25,702
Equity Securities, FV-NI, Gain (Loss), Total				$ 295,000

[1] Not within the scope of ASC 606