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		6 Months Ended			12 Months Ended
		Jun. 30, 2020		Jun. 30, 2019	Dec. 31, 2019
Loans past due 90 days or more and still accruing		$ 237	[1]	$ 50	$ 231	[1]
Ratio of loans past due 90 days or more and still accruing to loans, net of unearned income and deferred fees and costs		0.03%		0.01%	0.03%
Accruing restructured loans		$ 1,453		$ 1,954	$ 1,729
Impaired loans:
Impaired loans with no valuation allowance		4,151	[2]	5,167	4,174	[2]
Impaired loans with a valuation allowance		1,076	[2]	1,484	1,115	[2]
Total impaired loans		5,227	[2]	6,651	5,289	[2]
Valuation allowance		(104)		(129)	(110)
Impaired loans, net of allowance		5,123		6,522	5,179
Average recorded investment in impaired loans(1)	[2]	5,263		6,703	5,359
Interest income recognized on impaired loans, after designation as impaired		$ 29		$ 52	$ 171

[1] Only classes with past-due or nonaccrual loans are shown.

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