Note 3 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Loans Past Due 90 Days or More and Impaired Loans (Details) - USD ($) $ in Thousands		9 Months Ended			12 Months Ended
		Sep. 30, 2021		Sep. 30, 2020	Dec. 31, 2020
Loans past due 90 days or more and still accruing		$ 62		$ 236	$ 17
Ratio of loans past due 90 days or more and still accruing to loans, net of unearned income and deferred fees and costs		0.01%		0.03%	0.00%
Accruing restructured loans		$ 3,009		$ 1,426	$ 1,410
Impaired loans:
Impaired loans with no valuation allowance		6,084	[1]	3,939	3,858	[1]
Impaired loans with a valuation allowance		0	[1]	1,056	1,045	[1]
Total impaired loans		6,084	[1]	4,995	4,903	[1]
Valuation allowance		0		(104)	(75)
Impaired loans, net of allowance		6,084		4,891	4,828
Average recorded investment in impaired loans(1)	[1]	6,108		5,227	5,093
Interest income recognized on impaired loans, after designation as impaired		$ 175		$ 49	$ 54

[1] Recorded investment is net of charge-offs and interest paid while a loan is in nonaccrual status.