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, 2016		Dec. 31, 2015		Dec. 31, 2014	[5]
Loans past due 90 days or more and still accruing		$ 63	[1]	$ 156
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%
Accruing restructured loans		$ 3,769		$ 8,814
Impaired loans:
Impaired loans with no valuation allowance	[2]	8,269		12,973
Impaired loans with a valuation allowance	[2]	904		2,373
Total impaired loans	[2]	9,173		15,346
Valuation allowance		(26)		(45)
Impaired loans, net of allowance		9,147		15,301
Average recorded investment in impaired loans(1)	[4]	11,585	[3]	17,297	[3]	$ 16,311
Income recognized on impaired loans, after designation as impaired		553		769		$ 473
Amount of income recognized on a cash basis		$ 0		$ 0

[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.

[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.