Note 11 - Reconciliation of the Tax Provision (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation Of The Tax Provision [Abstract]
Provision at statutory rate									$ 4,825	$ 4,073	$ 3,673
Tax-exempt interest and dividend income									(948)	(1,033)	(1,126)
Bank-owned life insurance									(100)	(105)	(104)
Life insurance proceeds									(18)	0	0
Stock-based compensation expense									19	30	29
State income tax									82	41	34
Other									(14)	48	64
Net provision prior to tax reform adjustment									3,846	3,054	2,570
Deferred tax revaluation for change in tax rate - 2017 Tax Reform									2,054	0	0
Net provision	$ 2,993	$ 940	$ 845	$ 1,122	$ 743	$ 821	$ 702	$ 788	$ 5,900	$ 3,054	$ 2,570
Provision at statutory rate									34.00%	34.00%	34.00%
Tax-exempt interest and dividend income									(6.70%)	(8.60%)	(10.40%)
Bank-owned life insurance									(0.70%)	(0.90%)	(1.00%)
Life insurance proceeds									(0.10%)	(0.00%)	(0.00%)
Stock-based compensation expense									0.10%	0.30%	0.30%
State income tax									0.60%	0.30%	0.30%
Other									(0.10%)	0.40%	0.60%
Net provision prior to tax reform adjustment									27.10%	25.50%	23.80%
Deferred tax revaluation for change in tax rate - 2017 Tax Reform									14.50%	0.00%	0.00%
Net Provision									41.60%	25.50%	23.80%