Note 5 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Loans Past Due 90 Days or More and Impaired Loans (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017	[5]
Loans past due 90 days or more and still accruing	[1]	$ 231		$ 35
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%		0.00%
Accruing restructured loans		$ 1,729		$ 2,552
Impaired loans:
Impaired loans with no valuation allowance	[2]	4,174		5,667
Impaired loans with a valuation allowance	[2]	1,115		1,153
Total impaired loans	[2]	5,289		6,820
Valuation allowance		(110)		(139)
Impaired loans, net of allowance		5,179		6,681
Average recorded investment in impaired loans(1)	[3]	5,359	[4]	9,788	[4]	$ 13,344
Income recognized on impaired loans, after designation as impaired		171		250		$ 528
Amount of income recognized on a cash basis		$ 0		$ 0

[1] Only classes with past due or nonaccrual loans are presented

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

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

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

[5] Only classes with impaired loans are shown.