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, 2018		Dec. 31, 2017		Dec. 31, 2016	[5]
Loans past due 90 days or more and still accruing	[1]	$ 35		$ 51
Ratio of loans past due 90 days or more and still accruing to loans, net of unearned income and deferred fees and costs		0.00%		0.01%
Accruing restructured loans		$ 2,552		$ 5,134
Impaired loans:
Impaired loans with no valuation allowance	[2]	5,667		10,444
Impaired loans with a valuation allowance	[2]	1,153		1,480
Total impaired loans	[2]	6,820		11,924
Valuation allowance		(139)		(177)
Impaired loans, net of allowance		6,681		11,747
Average recorded investment in impaired loans(1)	[4]	9,788	[3]	13,344	[3]	$ 11,585
Income recognized on impaired loans, after designation as impaired		250		528		$ 553
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.